View Filing Data

Stock options and restricted stock units

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Entity Registrant Name	GLYCOMIMETICS INC
Entity Central Index Key	0001253689
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		43,137,227

Balance Sheets - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 219,828,634	$ 123,924,738
Prepaid expenses and other current assets	2,605,186	3,294,884
Total current assets	222,433,820	127,219,622
Property and equipment, net	968,551	1,106,899
Prepaid research and development expenses	1,714,971	204,364
Deposits	52,320	52,320
Total assets	225,169,662	128,583,205
Current liabilities:
Accounts payable	659,395	2,647,091
Accrued bonuses	1,293,254	1,883,051
Accrued expenses	4,388,938	3,566,607
Deferred rent	92,654	78,028
Total current liabilities	6,434,241	8,174,777
Deferred rent, net of current portion	639,733	707,003
Total liabilities	7,073,974	8,881,780
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding at September 30, 2018 and December 31, 2017
Common stock; $0.001 par value; 100,000,000 shares authorized, 43,137,227 shares issued and outstanding at September 30, 2018; 100,000,000 shares authorized, 34,359,799 shares issued and outstanding at December 31, 2017	43,136	34,358
Additional paid-in capital	404,696,376	271,944,173
Accumulated deficit	(186,643,824)	(152,277,106)
Total stockholders' equity	218,095,688	119,701,425
Total liabilities and stockholders' equity	$ 225,169,662	$ 128,583,205

Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Balance Sheets
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	43,137,227	34,359,799
Common stock, shares outstanding	43,137,227	34,359,799

Unaudited Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statements of Operations and Comprehensive Loss
Revenue
Costs and expenses:
Research and development expense	9,729,089	5,779,759	28,052,777	17,380,337
General and administrative expense	2,790,431	2,401,976	8,492,194	7,016,081
Total costs and expenses	12,519,520	8,181,735	36,544,971	24,396,418
Loss from operations	(12,519,520)	(8,181,735)	(36,544,971)	(24,396,418)
Other income	944,409	231,634	2,178,253	373,208
Net loss and comprehensive loss	$ (11,575,111)	$ (7,950,101)	$ (34,366,718)	$ (24,023,210)
Basic and diluted net loss per common share (in dollars per share)	$ (0.27)	$ (0.24)	$ (0.85)	$ (0.86)
Basic and diluted weighted average number of common shares (in shares)	43,069,282	32,724,010	40,345,071	27,814,781

Unaudited Statements of Cash Flows - USD ($)	9 Months Ended
Unaudited Statements of Cash Flows - USD ($)	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net loss	$ (34,366,718)	$ (24,023,210)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	206,794	193,976
Loss on disposal of property and equipment	168
Stock-based compensation expense	3,437,341	2,796,301
Changes in assets and liabilities
Prepaid expenses and other current assets	689,698	(537,244)
Prepaid research and development expenses	(1,510,607)
Accounts payable	(1,987,696)	66,512
Accrued expenses and bonuses	232,534	125,250
Deferred rent	(52,644)	(21,072)
Net cash used in operating activities	(33,351,130)	(21,399,487)
Investing activities
Purchases of property and equipment	(68,614)	(259,860)
Net cash used in investing activities	(68,614)	(259,860)
Financing activities
Proceeds from issuance of common stock, net of issuance costs	128,425,080	94,269,213
Proceeds from exercise of stock options and warrants	898,560	221,027
Net cash provided by financing activities	129,323,640	94,490,240
Net change in cash and cash equivalents	95,903,896	72,830,893
Cash and cash equivalents, beginning of period	123,924,738	40,041,641
Cash and cash equivalents, end of period	$ 219,828,634	$ 112,872,534

Description of the Business	9 Months Ended
Description of the Business	Sep. 30, 2018
Description of the Business
Description of the Business	GLYCOMIMETICS, INC. Notes to Unaudited Financial Statements 1. Description of the Business GlycoMimetics, Inc. (the Company), a Delaware corporation headquartered in Rockville, Maryland, was incorporated on April 4, 2003 and commenced operations on May 21, 2003. The Company is a clinical stage biotechnology company focused on the discovery and development of novel glycomimetic drugs to address unmet medical needs resulting from diseases in which carbohydrate biology plays a key role. Glycomimetics are molecules that mimic the structure of carbohydrates involved in important biological processes. The Company’s proprietary glycomimetics platform is based on its expertise in carbohydrate chemistry and its understanding of the role carbohydrates play in key biological processes. Using this expertise and understanding, the Company is developing a pipeline of proprietary glycomimetics designed to inhibit disease-related functions of carbohydrates, such as the roles they play in inflammation, cancer and infection. The Company’s executive personnel have devoted substantially all of their time to date to the planning and organization of the Company, the process of hiring scientists and other personnel, initiating and overseeing research and development programs, including planned and ongoing clinical trials, and securing adequate capital for anticipated growth and operations. The Company has not commercialized any of its drug candidates or commenced commercial operations. The Company is subject to a number of risks similar to those of other companies in similar development stages, including dependence on key individuals, the need to develop commercially viable drugs, the need to successfully compete with other companies, many of whom are larger and better capitalized, and the need to obtain adequate additional financing to fund the development of its drug candidates. The Company has incurred significant operating losses since inception and has relied on its ability to fund its operations through private and public equity financings, and management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, profitability will be dependent upon the successful development, approval and commercialization of its drug candidates and achieving a level of revenues adequate to support the Company’s cost structure. The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional capital. The Company believes that its currently available funds will be sufficient to fund the Company’s operations through at least 12 months from the date of the filing of this Quarterly Report. Management intends to fund future operations through additional public or private equity or debt offerings and potential future milestone payments from Pfizer (See Note 9) and may seek additional capital through arrangements with strategic partners or from other sources.

Significant Accounting Policies

9 Months Ended

Sep. 30, 2018

Summary of Significant Accounting Policies

Basis of Presentation and Significant Accounting Policies [Text Block]

2. Significant Accounting Policies

Basis of Accounting

The accompanying financial statements were prepared based on the accrual method of accounting in accordance with U.S. generally accepted accounting principles (GAAP).

Unaudited Financial Statements

The accompanying balance sheet as of September 30, 2018 and statements of operations and comprehensive loss for the three and nine months ended September 30, 2018 and 2017 and cash flows for the nine months ended September 30, 2018 and 2017 are unaudited. These unaudited financial statements have been prepared in accordance with the rules and regulations of the United States Securities and Exchange Commission (the SEC) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete annual financial statements. These financial statements should be read in conjunction with the audited financial statements and the accompanying notes for the year ended December 31, 2017 contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 6, 2018. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments (consisting of normal recurring adjustments) necessary to state fairly the Company’s financial position as of September 30, 2018, the results of operations for the three and nine months ended September 30, 2018 and 2017 and cash flows for the nine months ended September 30, 2018 and 2017. The December 31, 2017 balance sheet included herein was derived from audited financial statements, but does not include all disclosures including notes required by GAAP for complete annual financial statements. The financial data and other information disclosed in these notes to the financial statements related to the three and nine months ended September 30, 2018 and 2017 are unaudited. Interim results are not necessarily indicative of results for an entire year or for any future period.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Although actual results could differ from those estimates, management does not believe that such differences would be material.

Fair Value Measurements

The Company had no assets or liabilities that were measured using quoted prices for similar assets and liabilities or significant unobservable inputs (Level 2 and Level 3 assets and liabilities, respectively) as of September 30, 2018 and December 31, 2017. The carrying value of cash held in money market funds of $217.8 million and $121.9 million as of September 30, 2018 and December 31, 2017, respectively, is included in cash and cash equivalents and approximates market values based on quoted market prices (Level 1 inputs).

Concentration of Credit Risk

Credit risk represents the risk that the Company would incur a loss if counterparties failed to perform pursuant to the terms of their agreements. Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents. Cash and cash equivalents consist of money market funds with major financial institutions in the United States. These funds may be redeemed upon demand and, therefore, bear minimal risk. The Company does not anticipate any losses on such balances.

Revenue Recognition

Effective January 1, 2018, the Company adopted Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers (Topic 606), using the full retrospective transition method. Under this method, the Company would have been required to revise its financial statements, if applicable, for the years ended December 31, 2016 and 2017, and applicable interim periods within those years, as if Topic 606 had been effective for those periods. However, Topic 606 did not have any impact on the Company’s revenue recognition upon adoption. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration which the entity expects to receive in exchange for those goods and services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with the customer(s); (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods and services it transfers to the customer. At contract inception, the Company assesses the goods or services promised within each contract that falls under the scope of Topic 606, determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

License, Collaboration and Other Revenues

The Company enters into licensing agreements which are within the scope of Topic 606, under which it licenses certain of its product candidates’ rights to third parties. The terms of these arrangements typically include payment of one or more of the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; and royalties on net sales of the licensed product, which will be classified as royalty revenues, if and when earned.

In determining the appropriate amount of revenue to be recognized as it fulfills its obligation under each of its agreements, the Company performs the five steps described above. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement of personnel costs, discount rates and probabilities of technical and regulatory success.

Licensing of Intellectual Property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period, and, if necessary, adjusts the measure of performance and related revenue recognition.

Milestone Payments: At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal will not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration and other revenues and earnings in their period of adjustment.

Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and for which the license is deemed to be the predominant item to which royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue from its license agreements.

The Company has entered into a collaborative research and development agreement with Pfizer Inc. (Pfizer). The agreement is in the form of a license agreement (the Pfizer Agreement). The Pfizer Agreement calls for a non-refundable up-front payment and milestone payments upon achieving significant milestone events. The Pfizer Agreement also contemplates royalty payments on future sales of an approved product. There are no performance, cancellation, termination or refund provisions in the Pfizer Agreement that contain material financial consequences to the Company. For a complete discussion of the Company’s accounting for the Pfizer Agreement, see Note 9, “Research and License Agreements.”

Accrued Liabilities

The Company is required to estimate accrued liabilities as part of the process of preparing its financial statements. The estimation of accrued liabilities involves identifying services that have been performed on the Company’s behalf, and then estimating the level of service performed and the associated cost incurred for such services as of each balance sheet date. Accrued liabilities include professional service fees, such as for lawyers and accountants, contract service fees, such as those under contracts with clinical monitors, data management organizations and investigators in conjunction with clinical trials, and fees to contract manufacturers in conjunction with the production of clinical materials. Pursuant to the Company’s assessment of the services that have been performed, the Company recognizes these expenses as the services are provided. Such assessments include: (i) an evaluation by the project manager of the work that has been completed during the period; (ii) measurement of progress prepared internally and/or provided by the third-party service provider; (iii) analyses of data that justify the progress; and (iv) the Company’s judgment.

Research and Development Costs

Except for payments made in advance of services, research and development costs are expensed as incurred. For payments made in advance, the Company recognizes research and development expense as the services are rendered. Research and development costs primarily consist of salaries and related expenses for personnel, laboratory supplies and raw materials, sponsored research, depreciation of laboratory facilities and leasehold improvements, and utilities costs

related to research space. Other research and development expenses include fees paid to consultants and outside service providers including clinical research organizations and clinical manufacturing organizations.

Stock-Based Compensation

Stock-based payments are accounted for in accordance with the provisions of ASC 718, Compensation—Stock Compensation. The fair value of stock-based payments is estimated, on the date of grant, using the Black-Scholes-Merton model. The resulting fair value is recognized ratably over the requisite service period, which is generally the vesting period of the option.

The Company has elected to use the Black-Scholes-Merton option pricing model to value any options granted. The Company will reconsider use of the Black-Scholes-Merton model if additional information becomes available in the future that indicates another model would be more appropriate or if grants issued in future periods have characteristics that prevent their value from being reasonably estimated using this model.

A discussion of management’s methodology for developing some of the assumptions used in the valuation model follows:

Expected Dividend Yield—The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Expected Volatility—Volatility is a measure of the amount by which a financial variable such as share price has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. The Company utilizes the historical volatilities of a peer group (e.g., several public entities of similar size, complexity, and stage of development), along with the Company’s historical volatility since its initial public offering, to determine its expected volatility.

Risk-Free Interest Rate—This is the U.S. Treasury rate for the week of each option grant during the year, having a term that most closely resembles the expected life of the option.

Expected Term—This is a period of time that the options granted are expected to remain unexercised. Options granted have a maximum term of 10 years. The Company estimates the expected life of the option term to be 6.25 years. The Company uses a simplified method to calculate the average expected term.

Expected Forfeiture Rate—The Company accounts for forfeitures as they occur and does not make an estimate of expected forfeitures at the time of grant.

Net Loss Per Common Share

Basic net loss per common share is determined by dividing net loss by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock equivalents outstanding for the period. The treasury stock method is used to determine the dilutive effect of the Company’s stock options, restricted stock units and warrants.

Basic and diluted net loss per common share is computed as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Net loss	$	(11,575,111)	$	(7,950,101)	$	(34,366,718)	$	(24,023,210)
Basic and diluted net loss per common share	$	(0.27)	$	(0.24)	$	(0.85)	$	(0.86)
Basic and diluted weighted average common shares outstanding		43,069,282		32,724,010		40,345,071		27,814,781

The following potentially dilutive securities outstanding, at September 30, have been excluded from the computation of diluted weighted average common shares outstanding, as they would be anti-dilutive:

Comprehensive Loss

Comprehensive loss comprises net loss and other changes in equity that are excluded from net loss. For the three and nine months ended September 30, 2018 and 2017, the Company’s net loss equaled comprehensive net loss and, accordingly, no additional disclosure is presented.

Recently Issued Accounting Standards

Adopted Accounting Standards

In May 2014, the FASB issued Topic 606 which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. The Company adopted this new standard on January 1, 2018 using the full retrospective transition method. The Company evaluated the Pfizer Agreement to determine the impact of the new revenue standard on the up-front and milestone payments within the Pfizer Agreement and determined that the transition to the new revenue standard had no material impact on the prior financial statements presented. There were no financial statement line items affected by the transition. For further discussion on the adoption of this standard, see “Revenue Recognition” above and Note 9, “Research and License Agreements.”

In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805), Clarifying the Definition of a Business. The guidance changes the definition of a business to assist entities with evaluating when a set of transferred assets and activities is a business. The new guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The Company adopted this ASU as of January 1, 2018. The adoption of this ASU had no impact on the Company’s financial statements for the three and nine months ended September 30, 2018.

In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718), Scope of Modification Accounting, which clarifies when a change to the terms or conditions of a share-based payment award must be accounted for as a modification. The new guidance requires modification accounting if the fair value, vesting conditions or classification of the award is not the same immediately before and after a change to the terms and conditions of the award. The Company adopted this ASU on a prospective basis as of January 1, 2018. The adoption of this ASU had no impact on the Company’s financial statements for the three and nine months ended September 30, 2018.

Accounting Standards Not Yet Adopted

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which supersedes existing guidance on accounting for leases in Leases (Topic 840) and generally requires all leases, including operating leases, to be recognized in the statement of financial position as right-of-use assets and lease liabilities by lessees. The provisions of ASU 2016-02 are to be applied using a modified retrospective approach and are effective for reporting periods beginning after December 15, 2018; early adoption is permitted. The Company plans to elect the transition option provided under ASU 2018-11, which will not require adjustments to comparative periods nor require modified disclosures in those comparative periods. Upon adoption, the Company expects to elect the transition package of practical expedients permitted within the new standard, which among other things, allows the carryforward of the historical lease classification. Based on its anticipated election of practical expedients, the Company anticipates the recognition of right of use assets and related lease liabilities on its balance sheets related to its leases. The Company has engaged a professional services firm to assist in the implementation of ASC 842, and is completing its analysis of the impact of adopting ASC 842 on its statements of income and comprehensive income and balance sheets.

In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-based Payment Accounting, to simplify the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. The provisions of ASU 2018-07 are effective for reporting periods beginning after December 15, 2018, including interim periods within that fiscal year; early adoption is permitted, but no earlier than a company’s adoption date of Topic 606. Upon transition, the Company will be required to measure these nonemployee awards at fair value as of the adoption date. The Company had not early adopted this ASU as of September 30, 2018, but plans on adopting this ASU for its reporting period beginning January 1, 2019. The Company is currently evaluating the effect that this ASU will have on its financial statements.

With the exception of the new standards discussed above, there have been no new accounting pronouncements that have significance, or potential significance, to the Company’s financial statements.

Prepaid Expenses and Other Current Assets

9 Months Ended

Sep. 30, 2018

Prepaid Expenses and Other Current Assets

Prepaid Expenses and Other Current Assets

3. Prepaid Expenses and Other Current Assets

The following is a summary of the Company’s prepaid expenses and other current assets:


	September 30,		December 31,
	2018		2017
Prepaid research and development expenses	$	1,905,307	$	2,941,196
Other prepaid expenses		387,704		251,733
Other receivables		312,175		101,955
Prepaid expenses and other current assets	$	2,605,186	$	3,294,884

Property and Equipment

9 Months Ended

Sep. 30, 2018

Property and Equipment

Property and Equipment

4. Property and Equipment

Property and equipment, net consists of the following:


	September 30,		December 31,
	2018		2017
Furniture and fixtures	$	332,073	$	314,024
Laboratory equipment		1,342,973		1,325,667
Office equipment		11,085		11,085
Computer equipment		224,568		192,430
Leasehold improvements		573,165		573,165
Property and equipment		2,483,864		2,416,371
Less accumulated depreciation		(1,515,313)		(1,309,472)
Property and equipment, net	$	968,551	$	1,106,899

Depreciation expense was $68,477 and $70,060 for the three months ended September 30, 2018 and 2017, respectively, and $206,794 and $193,976 for the nine months ended September 30, 2018 and 2017, respectively.

Accrued Expenses

9 Months Ended

Sep. 30, 2018

Accrued Expenses

Accrued Expenses

5. Accrued Expenses

The following is a summary of the Company’s accrued expenses:


	September 30,		December 31,
	2018		2017
Accrued research and development expenses	$	3,390,096	$	2,702,445
Accrued consulting and other professional fees		363,067		227,811
Other accrued expenses		219,145		304,421
Accrued employee benefits		416,630		331,930
Accrued expenses	$	4,388,938	$	3,566,607

Operating Leases	9 Months Ended
Operating Leases	Sep. 30, 2018
Operating Leases
Operating Leases	6. Operating Leases The Company leases office and research space in Rockville, Maryland under an operating lease with a term through October 31, 2023 (as amended to date, the Lease) that is subject to annual rent increases. The Company has the right to sublease or assign all or a portion of the premises, subject to the conditions set forth in the Lease. The Lease may be terminated early by either the landlord or the Company in certain circumstances. In connection with the Lease, the Company received rent abatement as a lease incentive. The annual rent increases and rent abatement have been recognized as deferred rent that is being adjusted on a straight-line basis over the term of the Lease. In March 2016, the Company amended the Lease (the Lease Amendment) to lease additional space as of June 1, 2016. In addition to the other terms of the Lease, the Lease Amendment provided for a tenant improvement allowance reflected in the Company’s financial statements as an increase in capitalized leasehold improvements as incurred and an increase in deferred rent. In May 2016, the Company also paid a security deposit of $52,320 to be held until the expiration or termination of the Company’s obligations under the Lease. The term of the Lease Amendment for the additional space continues through October 31, 2023, the same date as for the premises originally leased under the Lease, subject to the Company’s renewal option set forth in the Lease. The Company’s one-time option to terminate the Lease effective as of October 31, 2020 also applies to the additional space. Deferred rent related to the Lease was $732,387 and $785,031 at September 30, 2018 and December 31, 2017, respectively. Total rent expense under the Company’s operating leases was $227,342 and $223,337 for the three months ended September 30, 2018 and 2017, respectively, and $673,416 and $667,507 for the nine months ended September 30, 2018 and 2017, respectively.

Stockholders' Equity

9 Months Ended

Sep. 30, 2018

Stockholders' Equity

Disclosure of stockholders' equity and share-based compensation

7. Stockholders’ Equity

Equity Offering

In March 2018, the Company completed a public offering in which the Company sold 8,050,000 shares of its common stock at a price to the public of $17.00 per share. The Company received net proceeds of $128.4 million from this offering, after deducting underwriting discounts, commissions and other offering expenses.

At-The-Market Sales Facility

On September 28, 2017, the Company entered into an at-the-market sales agreement (the “September 2017 Sales Agreement”) with Cowen and Company, LLC to sell up to $100.0 million of the Company’s common stock registered under a shelf registration statement filed with the U.S. Securities and Exchange Commission in September 2017. As of September 30, 2018, $80.0 million remained available to be sold under the terms of the September 2017 Sales Agreement. There were no shares sold under the September 2017 Sales Agreement during the nine months ended September 30, 2018.

Warrants to Acquire Common Stock

In connection with the prior issuance of convertible unsecured promissory notes, the Company issued warrants to purchase shares of common stock in 2008 and 2009. As of December 31, 2017, warrants to purchase an aggregate of 553,868 shares were outstanding, each with an exercise price of $0.33 per share. During the nine months ended September 30, 2018, all of the outstanding warrants were exercised; a total of 536,564 shares of common stock were issued to stockholders upon the net exercise of 546,709 outstanding warrants, and 7,159 shares of common stock were issued to stockholders upon the cash exercise of outstanding warrants, for total proceeds to the Company of $2,336. The Company no longer has any outstanding warrants to purchase shares of its capital stock.

2003 Stock Incentive Plan

The 2003 Stock Incentive Plan (the 2003 Plan) provided for the grant of incentives and nonqualified stock options and restricted stock awards. The exercise price for incentive stock options must be at least equal to the fair value of the common stock on the grant date. Unless otherwise stated in a stock option agreement, 25% of the shares subject to an option grant will vest upon the first anniversary of the vesting start date and thereafter at the rate of one forty-eighth of the option shares per month as of the first day of each month after the first anniversary. Upon termination of employment by reasons other than death, cause, or disability, any vested options shall terminate 60 days after the termination date. Stock options terminate 10 years from the date of grant. The 2003 Plan expired on May 21, 2013.

A summary of the Company’s stock option activity under the 2003 Plan for the nine months ended September 30, 2018 is as follows:



				Weighted-Average
				Remaining	Aggregate
	Outstanding	Weighted-Average		Contractual Term	Intrinsic Value
	Options	Exercise Price		(Years)	(In thousands)
Outstanding as of December 31, 2017	713,211	$	1.25	2.2
Options exercised	(43,131)		1.31
Options forfeited	—		—
Outstanding, Vested and Exercisable as of September 30, 2018	670,080		1.24	1.4	$	8,816

As of September 30, 2018, outstanding options under the 2003 Plan were fully expensed and all shares underlying outstanding options were fully vested. Total intrinsic value of the options exercised during the nine months ended September 30, 2018 and 2017 was $680,200 and $103,638, respectively, and total cash received for options exercised was $56,299 and $27,358 during the nine months ended September 30, 2018 and 2017, respectively. The total fair value of shares underlying options which vested in the nine months ended September 30, 2017 was $1,573.

2013 Equity Incentive Plan

The Company’s board of directors adopted, and its stockholders approved, its 2013 Equity Incentive Plan (the 2013 Plan) effective on January 9, 2014. The 2013 Plan provides for the grant of incentive stock options within the meaning of Section 422 of the Internal Revenue Code to the Company’s employees and its parent and subsidiary corporations’ employees, and for the grant of nonstatutory stock options, restricted stock awards, restricted stock unit awards, stock appreciation rights, performance stock awards and other forms of stock compensation to its employees, including officers, consultants and directors. The 2013 Plan also provides for the grant of performance cash awards to the Company’s employees, consultants and directors. Unless otherwise stated in a stock option agreement, 25% of the shares subject to an option grant will typically vest upon the first anniversary of the vesting start date and thereafter at the rate of one forty-eighth of the option shares per month as of the first day of each month after the first anniversary. Upon termination of employment by reasons other than death, cause, or disability, any vested options will terminate 90 days after the termination date, unless otherwise set forth in a stock option agreement. Stock options generally terminate 10 years from the date of grant.

Authorized Shares

The maximum number of shares of common stock that initially could be issued under the 2013 Plan was 1,000,000 shares, plus any shares subject to stock options or similar awards granted under the 2003 Plan that expire or terminate without having been exercised in full or are forfeited or repurchased by the Company. The number of shares of common stock reserved for issuance under the 2013 Plan automatically increases on January 1 of each year until January 1, 2023, by 3% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors. The maximum number of shares that may be issued pursuant to exercise of incentive stock options under the 2013 Plan is 20,000,000 shares. As of January 1, 2018, the number of shares of common stock that may be issued under the 2013 Plan was automatically increased by 1,030,793 shares, representing 3% of the total number of shares of common stock outstanding on December 31, 2017, increasing the number of shares of common stock available for issuance under the 2013 Plan to 3,867,994 shares.

Shares issued under the 2013 Plan may be authorized but unissued or reacquired shares of common stock. Shares subject to stock awards granted under the 2013 Plan that expire or terminate without being exercised in full, or that are paid out in cash rather than in shares, will not reduce the number of shares available for issuance under the 2013 Plan. Additionally, shares issued pursuant to stock awards under the 2013 Plan that the Company repurchases or that are forfeited, as well as shares reacquired by the Company as consideration for the exercise or purchase price of a stock award or to satisfy tax withholding obligations related to a stock award, will become available for future grant under the 2013 Plan.

A summary of the Company’s stock option activity under the 2013 Plan for the nine months ended September 30, 2018 is as follows:


				Weighted-Average
				Remaining	Aggregate
	Outstanding	Weighted-Average		Contractual Term	Intrinsic Value
	Options	Exercise Price		(Years)	(In thousands)
Outstanding as of December 31, 2017	2,664,163	$	7.34	7.4
Options granted	812,979		19.53
Options exercised	(123,658)		6.79
Options forfeited	(52,035)		13.02
Outstanding as of September 30, 2018	3,301,449		8.44	7.3	$	21,243
Vested or expected to vest as of September 30, 2018	3,301,449		8.44	7.3	$	21,243
Exercisable as of September 30, 2018	1,940,699		7.72	6.3	$	13,014

The weighted-average fair value of the options granted during the nine months ended September 30, 2018 and 2017 was $13.11 per share and $4.76 per share, respectively, applying the Black-Scholes-Merton option pricing model utilizing the following weighted-average assumptions:


	Nine Months Ended	Nine Months Ended
	September 30, 2018	September 30, 2017
Expected term	6.25 years	6.25 years
Expected volatility	73.83%	75.20%
Risk-free interest rate	2.53%	2.08%
Expected dividend yield	0%	0%

As of September 30, 2018, there was $10,599,842 of total unrecognized compensation expense related to unvested options under the 2013 Plan that will be recognized over a weighted-average period of approximately 2.9 years. Total intrinsic value of the options exercised during the nine months ended September 30, 2018 and 2017 was $1,243,400 and $228,291, respectively, and total cash received for options exercised was $839,924 and $193,669 during the nine months September 30, 2018 and 2017, respectively. The total fair value of shares underlying options which vested in the nine months ended September 30, 2018 and 2017 was $2,611,141 and $2,872,004, respectively.

A restricted stock unit (RSU) is a stock award that entitles the holder to receive shares of the Company’s common stock as the award vests. The fair value of each RSU is based on the closing price of the Company’s common stock on the date of grant. The Company has granted RSUs with service conditions (service RSUs) that vest in three equal annual installments provided that the employee remains employed with the Company at each installment date. As of September 30, 2018, there was $6,715 of unrecognized compensation costs related to unvested service RSUs.

The following is a summary of RSU activity under the 2013 Plan for the nine months ended September 30, 2018:



			Weighted-Average
		Number of Shares	Grant Date
	Underlying RSUs			Fair Value
Unvested at December 31, 2017		9,667	$	4.61
Granted		—		—
Forfeited		—		—
Vested		4,834		4.61
Unvested at September 30, 2018		4,833		4.61

Stock-based compensation expense was classified on the statements of operations as follows for the three and nine months ended September 30, 2018 and 2017:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development expense	$	429,477	$	327,133	$	1,282,040	$	953,821
General and administrative expense		741,646		635,212		2,155,301		1,842,480
Total stock-based compensation expense	$	1,171,123	$	962,345	$	3,437,341	$	2,796,301

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2018
Income Taxes
Income Taxes	8. Income Taxes On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJA”) was enacted into law. The TCJA contains several key tax provisions including the reduction of the corporate income tax rate from 35% to 21% effective January 1, 2018, as well as a variety of other changes, including the limitation of the tax deductibility of interest expense, acceleration of expensing of certain business assets and reductions in the amount of executive pay that can qualify as a tax deduction. ASC 740 requires the Company to recognize the effect of the tax law changes in the period of enactment. The Company re-measured certain of its U.S. deferred tax assets and liabilities, based on the rates at which they are expected to reverse in the future. The tax benefit related to the re-measurement of the deferred tax balance was $15.2 million as of December 31, 2017, which was offset by the related valuation allowance. The SEC staff has issued Staff Accounting Bulletin (“SAB”) 118, which will allow the Company to record provisional amounts during a measurement period which is similar to the measurement period used when accounting for business combinations. While the Company has substantially completed the provisional analysis of the income tax effects of this recent tax reform legislation, and recorded a reasonable estimate of such effects, the ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, further refinement of the Company’s calculations, additional analysis, changes in assumptions, and actions the Company may take as a result of the TCJA. During the three and nine months ended September 30, 2018, the Company did not make any adjustments to its provisional amounts. The Company has not recorded any tax provision or benefit for the nine months ended September 30, 2018 and 2017. The Company has provided a valuation allowance for the full amount of its net deferred tax assets since realization of any future benefit from deductible temporary differences, net operating loss carryforwards and research and development credits is not more-likely-than-not to be realized at September 30, 2018 and December 31, 2017.

Research and License Agreements	9 Months Ended
Research and License Agreements	Sep. 30, 2018
Research And License Agreements [Abstract]
Research and License Agreement	9. Research and License Agreements In October 2011, the Company and Pfizer entered into the Pfizer Agreement that provides Pfizer an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease and for other diseases for which the drug candidate may be developed. The Company was responsible for completion of the Phase 2 clinical trial, after which Pfizer assumed all further development and commercialization responsibilities. Upon execution of the Pfizer Agreement, the Company received an up-front payment of $22.5 million. The Pfizer Agreement also provides for potential milestone payments of up to $115.0 million upon the achievement of specified development milestones, including the dosing of the first patients in Phase 3 clinical trials for up to two indications and the first commercial sale of a licensed product in the United States and selected European countries for up to two indications; potential milestone payments of up to $70.0 million upon the achievement of specified regulatory milestones, including the acceptance of our filings for regulatory approval by regulatory authorities in the United States and Europe for up to two indications; and potential milestone payments of up to $135.0 million upon the achievement of specified levels of annual net sales of licensed products. Pfizer has the right to terminate the Pfizer Agreement by giving prior written notice. In May 2014, Pfizer made a $15.0 million non-refundable milestone payment to the Company, which was recognized as revenue by the Company in May 2014 when earned. In June 2015, Pfizer dosed the first patient in the Phase 3 clinical trial of rivipansel, which triggered a non-refundable milestone payment to the Company of $20.0 million, which the Company recognized as revenue in June 2015. The Company did not recognize any revenue under the Pfizer Agreement during the nine months ended September 30, 2018 or 2017. The Company assessed this arrangement in accordance with Topic 606 and concluded that the contract counterparty, Pfizer, is a customer. The Company identified the following performance obligations under the contract: (1) an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease and for other diseases for which the drug candidate may be developed; and (2) research and development (R&D) services to develop the rivipansel compound for commercial use related to the Phase 2 clinical trial and delivery of data to Pfizer. In addition to the rivipansel license and R&D services, management also considered whether the Company’s participation in a Joint Steering Committee (JSC) constituted a promise. The JSC was formed solely for communication purposes between Pfizer and the Company relating to Pfizer’s progress in further developing rivipansel for commercial use. The Company’s involvement in the JSC is limited to attending the JSC meetings on a semi-annual basis to receive progress updates from Pfizer; Pfizer is responsible for calling and organizing the meetings. Given the minimal level of involvement by the Company, participation in the JSC is not considered a significant aspect of the arrangement and the related costs, such as employee time, are not material. Therefore, management views the Company’s participation in JSC as administrative only and did not further evaluate its participation in the JSC in identifying the performance obligations in the Pfizer Agreement. Under the Pfizer Agreement, in order to evaluate the appropriate transaction price, the Company determined that the up-front amount constituted the entirety of the consideration to be included in the transaction price and to be allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. The transaction price of the up-front fee is equal to the $22.5 million received. The fixed up-front consideration is recognized under ASC 606 based on when control of the combined performance obligation is transferred to the customer, which corresponds with the service period (through March 2013). None of the clinical or regulatory milestones have been included in the transaction price, as all milestone amounts were fully constrained. Event-driven milestones are a form of variable consideration as the payments are variable based on the occurrence of future events. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and is contingent upon success in future clinical trials and the licensee’s efforts. Recognition of event-driven milestones should be recognized when the variable consideration is no longer constrained. There are no changes in accounting necessary for the $15.0 million milestone payment recognized in May 2014 or the $20.0 million milestone payment recognized in June 2015 as a result of Pfizer dosing the first patient in the Phase 3 clinical trial of rivipansel. Future event-driven milestones will be recognized when the constraint no longer applies. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to Pfizer and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. In evaluating the Pfizer Agreement, the Company considered that there were no significant financing components identified, no non-cash consideration was paid by Pfizer and no consideration was paid by the Company to Pfizer as part of the arrangement. The Company has entered into a research services agreement (the Research Agreement) with the University of Basel (the University) for biological evaluation of selectin antagonists. While the scope of work under the Research Agreement with the University ended in 2017, certain patents covering the rivipansel compound are subject to provisions of the Research Agreement. Under the terms of the Research Agreement, the Company owes to the University 10% of all future milestone and royalty payments received from Pfizer with respect to rivipansel. There were no milestone payments due to the University for the nine months ended September 30, 2018 or 2017.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2018

Summary of Significant Accounting Policies

Basis of Accounting

The accompanying financial statements were prepared based on the accrual method of accounting in accordance with U.S. generally accepted accounting principles (GAAP).

Unaudited Financial Statements

Use of Estimates

Fair Value Measurements

Concentration of Credit Risk

Revenue Recognition

License, Collaboration and Other Revenues

Accrued Liabilities

Research and Development Costs

Stock-Based Compensation

A discussion of management’s methodology for developing some of the assumptions used in the valuation model follows:

Expected Dividend Yield—The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Risk-Free Interest Rate—This is the U.S. Treasury rate for the week of each option grant during the year, having a term that most closely resembles the expected life of the option.

Expected Forfeiture Rate—The Company accounts for forfeitures as they occur and does not make an estimate of expected forfeitures at the time of grant.

Net Loss Per Common Share

Basic and diluted net loss per common share is computed as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Net loss	$	(11,575,111)	$	(7,950,101)	$	(34,366,718)	$	(24,023,210)
Basic and diluted net loss per common share	$	(0.27)	$	(0.24)	$	(0.85)	$	(0.86)
Basic and diluted weighted average common shares outstanding		43,069,282		32,724,010		40,345,071		27,814,781

Comprehensive Loss

Recently Issued Accounting Standards

Adopted Accounting Standards

Accounting Standards Not Yet Adopted

With the exception of the new standards discussed above, there have been no new accounting pronouncements that have significance, or potential significance, to the Company’s financial statements.

Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2018

Net Loss Per Share of Common Stock

Computation of basic and diluted net loss per common share


	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Net loss	$	(11,575,111)	$	(7,950,101)	$	(34,366,718)	$	(24,023,210)
Basic and diluted net loss per common share	$	(0.27)	$	(0.24)	$	(0.85)	$	(0.86)
Basic and diluted weighted average common shares outstanding		43,069,282		32,724,010		40,345,071		27,814,781

Potentially dilutive securities outstanding

Prepaid Expenses and Other Current Assets (Tables)

9 Months Ended

Sep. 30, 2018

Prepaid Expenses and Other Current Assets

Summary of Prepaid Expenses and Other Current Assets

The following is a summary of the Company’s prepaid expenses and other current assets:


	September 30,		December 31,
	2018		2017
Prepaid research and development expenses	$	1,905,307	$	2,941,196
Other prepaid expenses		387,704		251,733
Other receivables		312,175		101,955
Prepaid expenses and other current assets	$	2,605,186	$	3,294,884

Property and Equipment (Tables)

9 Months Ended

Sep. 30, 2018

Property and Equipment

Summary of Property and Equipment, Net

Property and equipment, net consists of the following:


	September 30,		December 31,
	2018		2017
Furniture and fixtures	$	332,073	$	314,024
Laboratory equipment		1,342,973		1,325,667
Office equipment		11,085		11,085
Computer equipment		224,568		192,430
Leasehold improvements		573,165		573,165
Property and equipment		2,483,864		2,416,371
Less accumulated depreciation		(1,515,313)		(1,309,472)
Property and equipment, net	$	968,551	$	1,106,899

Accrued Expenses (Tables)

9 Months Ended

Sep. 30, 2018

Accrued Expenses

Summary of Accrued Expenses


	September 30,		December 31,
	2018		2017
Accrued research and development expenses	$	3,390,096	$	2,702,445
Accrued consulting and other professional fees		363,067		227,811
Other accrued expenses		219,145		304,421
Accrued employee benefits		416,630		331,930
Accrued expenses	$	4,388,938	$	3,566,607

Stockholders Equity (Tables)

9 Months Ended

Sep. 30, 2018

Stock-Based Compensation Expense


	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development expense	$	429,477	$	327,133	$	1,282,040	$	953,821
General and administrative expense		741,646		635,212		2,155,301		1,842,480
Total stock-based compensation expense	$	1,171,123	$	962,345	$	3,437,341	$	2,796,301

2003 Stock Incentive Plan

Company's Stock Option Activity

A summary of the Company’s stock option activity under the 2003 Plan for the nine months ended September 30, 2018 is as follows:



				Weighted-Average
				Remaining	Aggregate
	Outstanding	Weighted-Average		Contractual Term	Intrinsic Value
	Options	Exercise Price		(Years)	(In thousands)
Outstanding as of December 31, 2017	713,211	$	1.25	2.2
Options exercised	(43,131)		1.31
Options forfeited	—		—
Outstanding, Vested and Exercisable as of September 30, 2018	670,080		1.24	1.4	$	8,816

2013 Equity Incentive Plan

Company's Stock Option Activity

A summary of the Company’s stock option activity under the 2013 Plan for the nine months ended September 30, 2018 is as follows:


				Weighted-Average
				Remaining	Aggregate
	Outstanding	Weighted-Average		Contractual Term	Intrinsic Value
	Options	Exercise Price		(Years)	(In thousands)
Outstanding as of December 31, 2017	2,664,163	$	7.34	7.4
Options granted	812,979		19.53
Options exercised	(123,658)		6.79
Options forfeited	(52,035)		13.02
Outstanding as of September 30, 2018	3,301,449		8.44	7.3	$	21,243
Vested or expected to vest as of September 30, 2018	3,301,449		8.44	7.3	$	21,243
Exercisable as of September 30, 2018	1,940,699		7.72	6.3	$	13,014

Weighted-Average Fair Value of Options Granted


	Nine Months Ended	Nine Months Ended
	September 30, 2018	September 30, 2017
Expected term	6.25 years	6.25 years
Expected volatility	73.83%	75.20%
Risk-free interest rate	2.53%	2.08%
Expected dividend yield	0%	0%

Summary of RSU Activity

The following is a summary of RSU activity under the 2013 Plan for the nine months ended September 30, 2018:



			Weighted-Average
		Number of Shares	Grant Date
	Underlying RSUs			Fair Value
Unvested at December 31, 2017		9,667	$	4.61
Granted		—		—
Forfeited		—		—
Vested		4,834		4.61
Unvested at September 30, 2018		4,833		4.61

Significant Accounting Policies (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Share-based Compensation
Expected term	6 years 3 months
Level 1
Fair Value Measurements
Carrying value of cash held in money market fund	$ 217.8	$ 121.9
Level 2
Fair Value Measurements
Assets measured at fair value levels 2 or 3	0.0	0.0
Liabilities measured at fair value levels 2 or 3	0.0	0.0
Level 3
Fair Value Measurements
Assets measured at fair value levels 2 or 3	0.0	0.0
Liabilities measured at fair value levels 2 or 3	$ 0.0	$ 0.0
Maximum
Share-based Compensation
Expiration period	10 years

Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Summary of Significant Accounting Policies
Net loss	$ (11,575,111)	$ (7,950,101)	$ (34,366,718)	$ (24,023,210)
Earnings Per Share, Basic and Diluted	$ (0.27)	$ (0.24)	$ (0.85)	$ (0.86)
Basic and diluted weighted average common shares outstanding	43,069,282	32,724,010	40,345,071	27,814,781

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Significant Accounting Policies - Potentially Dilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Warrants [Member]
Anti-dilutive securities		553,868
Stock Options and Restricted Stock Units [Member]
Anti-dilutive securities	3,976,362	3,421,124

Significant Accounting Policies - Recently Issued Accounting Standards (Detail) - USD ($)	Sep. 30, 2018	Jan. 01, 2018
ASU 2014-09
New accounting pronouncement, modified retrospective method
Cumulative effect adjustment for full retrospective transition		$ 0
ASU 2017-01
New accounting pronouncement, modified retrospective method
Impact of adoption on financial statements	$ 0
ASU 2017-09
New accounting pronouncement, modified retrospective method
Impact of adoption on financial statements	$ 0

Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets
Prepaid research and development expenses	$ 1,905,307	$ 2,941,196
Other prepaid expenses	387,704	251,733
Other receivables	312,175	101,955
Prepaid expenses and other current assets	$ 2,605,186	$ 3,294,884

Property and Equipment (Detail) - USD ($)	3 Months Ended		9 Months Ended
Property and Equipment (Detail) - USD ($)	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,483,864		$ 2,483,864		$ 2,416,371
Less accumulated depreciation	(1,515,313)		(1,515,313)		(1,309,472)
Property and equipment, net	968,551		968,551		1,106,899
Depreciation of property and equipment	68,477	$ 70,060	206,794	$ 193,976
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	332,073		332,073		314,024
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	1,342,973		1,342,973		1,325,667
Office Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	11,085		11,085		11,085
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	224,568		224,568		192,430
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 573,165		$ 573,165		$ 573,165

Accrued Expenses - Summary of Accrued Expenses (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Accrued Expenses
Accrued research and development expenses	$ 3,390,096	$ 2,702,445
Accrued consulting and other professional fees	363,067	227,811
Other accrued expenses	219,145	304,421
Accrued employee benefits	416,630	331,930
Accrued expenses	$ 4,388,938	$ 3,566,607

Operating Leases (Details) - USD ($)	3 Months Ended		9 Months Ended
Operating Leases (Details) - USD ($)	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	May 31, 2016
Deferred Rent Credit	$ 732,387		$ 732,387		$ 785,031
Operating leases, rent expense	227,342	$ 223,337	673,416	$ 667,507
Security deposit paid	$ 52,320		$ 52,320		$ 52,320
Rockville
Security deposit paid						$ 52,320

Stockholders' Equity - Equity Offerings (Detail) - Common Stock - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Sep. 28, 2017
September 2017 Sales Agreement
Equity offerings
Common stock available for sale under agreement		$ 80.0
Securities sold during period		0
September 2017 Sales Agreement \| Maximum
Equity offerings
Common stock available for sale under agreement			$ 100.0
Public Equity Offering
Equity offerings
Issuance of common stock, net of issuance costs, shares	8,050,000
Weighted average price per share issued	$ 17.00
Aggregate net proceeds from stock sale	$ 128.4

Stockholders' Equity - Common Stock Warrants (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Number of warrants exercised	546,709
Proceeds from cash exercise of warrants	$ 2,336
Common stock warrants outstanding	0
Common Stock
Class of Warrant or Right [Line Items]
Number of shares underlying outstanding warrants		553,868
Exercise price per share		$ 0.33
Shares issued upon net exercise of outstanding warrants	536,564
Shares issued upon cash exercise of warrants	7,159

Stockholders' Equity - Incentive Plans (Detail) - USD ($)			9 Months Ended
	Jan. 01, 2018	Jan. 09, 2014	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Maximum
Incentive plans
Expiration period			10 years
2003 Stock Incentive Plan
Incentive plans
Period from date of termination that any vested options shall expire			60 days
Expiration period			10 years
Intrinsic value of options exercised			$ 680,200	$ 103,638
Cash proceeds from exercise of stock options			$ 56,299	27,358
Options exercised			43,131
Fair value of shares vested				1,573
2003 Stock Incentive Plan \| Upon first anniversary of start date
Incentive plans
Percent of shares subject to option grant that will vest			25.00%
2003 Stock Incentive Plan \| Each month after the first anniversary
Incentive plans
Percent of shares subject to option grant that will vest			2.083%
2013 Equity Incentive Plan
Incentive plans
Period from date of termination that any vested options shall expire		90 days
Expiration period		10 years
Unrecognized compensation expense related to unvested options			$ 10,599,842
Period for unrecognized compensation expense related to unvested options yet has not been recognized			2 years 10 months 24 days
Intrinsic value of options exercised			$ 1,243,400	228,291
Cash proceeds from exercise of stock options			$ 839,924	193,669
Options exercised			123,658
Fair value of shares vested			$ 2,611,141	$ 2,872,004
2013 Equity Incentive Plan \| Upon first anniversary of start date
Incentive plans
Percent of shares subject to option grant that will vest		25.00%
2013 Equity Incentive Plan \| Each month after the first anniversary
Incentive plans
Percent of shares subject to option grant that will vest		2.083%
Common Stock \| 2013 Equity Incentive Plan
Authorized shares
Common stock authorized under 2013 plan	3,867,994	1,000,000
Automatic increase in number of shares reserved for issuance as a percentage of the total common stock outstanding at the end of the prior year		3.00%			3.00%
Maximum number of shares that may be issued pursuant to exercise of incentive stock		20,000,000
Increase in number of shares of common stock	1,030,793

Stockholders' Equity - Company's Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
2003 Stock Incentive Plan
OUTSTANDING OPTIONS
Outstanding at beginning of period	713,211
Options exercised	(43,131)
Outstanding at end of period	670,080	713,211
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period	$ 1.25
Options exercised	1.31
Outstanding at end of period	$ 1.24	$ 1.25
VESTED AND EXPECTED TO VEST
Aggregate Intrinsic Value (in thousands)	$ 8,816
ADDITIONAL DISCLOSURES
Aggregate intrinsic value (in thousands) exercisable at end of period	$ 8,816
Weighted-average contractual term outstanding	1 year 4 months 24 days	2 years 2 months 12 days
Aggregate intrinsic value (in thousands) outstanding at end of period	$ 8,816
2013 Equity Incentive Plan
OUTSTANDING OPTIONS
Outstanding at beginning of period	2,664,163
Options granted	812,979
Options exercised	(123,658)
Options forfeited	(52,035)
Outstanding at end of period	3,301,449	2,664,163
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period	$ 7.34
Options granted	19.53
Options exercised	6.79
Options forfeited	13.02
Outstanding at end of period	$ 8.44	$ 7.34
VESTED AND EXPECTED TO VEST
Outstanding options	3,301,449
Weighted-Average Exercise Price	$ 8.44
Weighted-Average Remaining Contractual Term	7 years 3 months 18 days
Aggregate Intrinsic Value (in thousands)	$ 21,243
ADDITIONAL DISCLOSURES
Outstanding options exercisable at end of period	1,940,699
Weighted-average exercise price exercisable at end of period	$ 7.72
Weighted-average contractual term (years) exercisable at end of period	6 years 3 months 18 days
Aggregate intrinsic value (in thousands) exercisable at end of period	$ 13,014
Weighted-average contractual term outstanding	7 years 3 months 18 days	7 years 4 months 24 days
Aggregate intrinsic value (in thousands) outstanding at end of period	$ 21,243

Stockholders' Equity - Weighted-Average assumptions (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Weighted-average assumptions
Expected term	6 years 3 months
2013 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value of the options granted	$ 13.11	$ 4.76
Weighted-average assumptions
Expected term	6 years 3 months	6 years 3 months
Expected volatility	73.83%	75.20%
Risk-free interest rate	2.53%	2.08%
Expected dividend yield	0.00%	0.00%

Stockholders' Equity - Summary of RSU Activity (Detail) - RSU [Member] - 2013 Equity Incentive Plan	9 Months Ended
	Sep. 30, 2018 USD ($) installment $ / shares shares
Restricted Stock Units information
Unrecognized compensation expense related to unvested service RSUs \| $	$ 6,715
Number of vesting installments \| installment	3
NUMBER OF SHARES
Unvested at beginning of period \| shares	9,667
Granted \| shares	0
Forfeited \| shares	0
Vested \| shares	4,834
Unvested at end of period \| shares	4,833
WEIGHTED-AVERAGE GRANT DATE FAIR VALUE
Unvested at beginning of period \| $ / shares	$ 4.61
Granted \| $ / shares	0.00
Forfeited \| $ / shares	0.00
Vested \| $ / shares	4.61
Unvested at end of period \| $ / shares	$ 4.61

Stockholders' Equity - Stock-Based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-based compensation expense
Total stock-based compensation expense	$ 1,171,123	$ 962,345	$ 3,437,341	$ 2,796,301
Research and Development
Stock-based compensation expense
Total stock-based compensation expense	429,477	327,133	1,282,040	953,821
General and Administrative Expense.
Stock-based compensation expense
Total stock-based compensation expense	$ 741,646	$ 635,212	$ 2,155,301	$ 1,842,480

Income Taxes - 10-Q (Details) - USD ($)			9 Months Ended		12 Months Ended
Income Taxes - 10-Q (Details) - USD ($)	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes
Income tax (benefit) provision			$ 0	$ 0
Effect of Tax Cuts and Jobs Act of 2017 Accounting Incomplete Provisional [Abstract]
U.S. Federal statutory tax rate	21.00%				35.00%
Tax benefit related to remeasurement		$ 15,200,000
Valuation allowance offset to remeasurement tax benefit		$ 15,200,000

Research and License Agreements - Additional Information (Detail)	1 Months Ended			3 Months Ended		9 Months Ended
	Jun. 30, 2015 USD ($)	May 31, 2014 USD ($)	Oct. 31, 2011 USD ($) item	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)
Research and License Agreements
Revenue	$ 20,000,000	$ 15,000,000
Number of milestones included in transaction price \| item						0
License Agreement \| Pfizer
Research and License Agreements
Up-front payment received			$ 22,500,000
Revenue						$ 0	0
Transaction price						22,500,000
Research Services Agreement \| University Of Basel
Research and License Agreements
Milestone payment obligation				$ 0	$ 0	$ 0	$ 0
Royalty payment due against license fees received (as a percent)						10.00%
Achievement Of Specified Development Milestone \| License Agreement \| Pfizer
Research and License Agreements
Non-refundable milestone payment received	$ 20,000,000	$ 15,000,000
Achievement Of Specified Development Milestone \| License Agreement \| Pfizer \| Maximum
Research and License Agreements
Potential milestone payments			$ 115,000,000
Number of indications \| item			2
Achievement Of Specified Regulatory Milestone \| License Agreement \| Pfizer \| Maximum
Research and License Agreements
Potential milestone payments			$ 70,000,000
Number of indications \| item			2
Achievement Of Specified Levels Of Annual Net Sales Of Licensed Products \| License Agreement \| Pfizer \| Maximum
Research and License Agreements
Potential milestone payments			$ 135,000,000