GlycoMimetics (GLYC) 10-Q 7 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 04, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Sep. 30, 2019
Entity Registrant Name	GLYCOMIMETICS INC
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		43,359,949
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001253689
Current Fiscal Year End Date	--12-31
Amendment Flag	false

Balance Sheets

Balance Sheets - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 170,886,792	$ 209,917,595
Prepaid expenses and other current assets	3,909,979	2,351,524
Total current assets	174,796,771	212,269,119
Property and equipment, net	878,406	957,226
Prepaid research and development expenses	1,560,607	1,560,607
Deposits	52,320	52,320
Operating lease right-of-use asset	3,166,539
Total assets	180,454,643	214,839,272
Current liabilities:
Accounts payable	1,407,548	2,663,579
Accrued bonuses	1,645,619	1,727,184
Accrued expenses	6,599,247	4,273,620
Operating lease liabilities	783,925
Deferred rent		98,771
Total current liabilities	10,436,339	8,763,154
Noncurrent operating lease liabilities	2,937,327
Deferred rent, net of current portion		611,623
Total liabilities	13,373,666	9,374,777
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding at September 30, 2019 and December 31, 2018
Common stock; $0.001 par value; 100,000,000 shares authorized, 43,359,949 shares issued and outstanding at September 30, 2019; 100,000,000 shares authorized, 43,160,751 shares issued and outstanding at December 31, 2018	43,358	43,159
Additional paid-in capital	410,753,952	405,972,075
Accumulated deficit	(243,716,333)	(200,550,739)
Total stockholders' equity	167,080,977	205,464,495
Total liabilities and stockholders' equity	$ 180,454,643	$ 214,839,272

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
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	43,359,949	43,160,751
Common stock, shares outstanding	43,359,949	43,160,751

Unaudited Statements of Operati

Unaudited Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statements of Operations and Comprehensive Loss
Revenue
Costs and expenses:
Research and development expense	10,724,178	9,729,089	35,562,202	28,052,777
General and administrative expense	3,380,932	2,790,431	10,491,991	8,492,194
Total costs and expenses	14,105,110	12,519,520	46,054,193	36,544,971
Loss from operations	(14,105,110)	(12,519,520)	(46,054,193)	(36,544,971)
Interest income	853,228	944,409	2,888,599	2,178,253
Net loss and comprehensive loss	$ (13,251,882)	$ (11,575,111)	$ (43,165,594)	$ (34,366,718)
Basic and diluted net loss per common share (in dollars per share)	$ (0.31)	$ (0.27)	$ (1)	$ (0.85)
Basic and diluted weighted average number of common shares (in shares)	43,295,397	43,069,282	43,215,125	40,345,071

Unaudited Statements of Stockho

Unaudited Statements of Stockholders' Equity - USD ($)	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2017	$ 34,358	$ 271,944,173	$ (152,277,106)	$ 119,701,425
Balance, shares at Dec. 31, 2017	34,359,799
Issuance of common stock, net of issuance costs	$ 8,050	128,417,030		128,425,080
Issuance of common stock, net of issuance costs, shares	8,050,000
Exercise of options and warrants	$ 728	897,832		898,560
Exercise of options and warrants, shares	727,428
Stock-based compensation		3,437,341		3,437,341
Net loss			(34,366,718)	(34,366,718)
Balance at Sep. 30, 2018	$ 43,136	404,696,376	(186,643,824)	218,095,688
Balance, shares at Sep. 30, 2018	43,137,227
Balance at Jun. 30, 2018	$ 43,054	403,020,562	(175,068,713)	227,994,903
Balance, shares at Jun. 30, 2018	43,055,424
Exercise of options and warrants	$ 82	504,691		504,773
Exercise of options and warrants, shares	81,803
Stock-based compensation		1,171,123		1,171,123
Net loss			(11,575,111)	(11,575,111)
Balance at Sep. 30, 2018	$ 43,136	404,696,376	(186,643,824)	218,095,688
Balance, shares at Sep. 30, 2018	43,137,227
Balance at Dec. 31, 2018	$ 43,159	405,972,075	(200,550,739)	205,464,495
Balance, shares at Dec. 31, 2018	43,160,751
Exercise of options	$ 199	292,892		293,091
Exercise of options, shares	199,198
Stock-based compensation		4,488,985		4,488,985
Net loss			(43,165,594)	(43,165,594)
Balance at Sep. 30, 2019	$ 43,358	410,753,952	(243,716,333)	167,080,977
Balance, shares at Sep. 30, 2019	43,359,949
Balance at Jun. 30, 2019	$ 43,192	408,980,202	(230,464,451)	178,558,943
Balance, shares at Jun. 30, 2019	43,193,190
Exercise of options	$ 166	186,603		186,769
Exercise of options, shares	166,759
Stock-based compensation		1,587,147		1,587,147
Net loss			(13,251,882)	(13,251,882)
Balance at Sep. 30, 2019	$ 43,358	$ 410,753,952	$ (243,716,333)	$ 167,080,977
Balance, shares at Sep. 30, 2019	43,359,949

Unaudited Statements of Cash Fl

Unaudited Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities
Net loss	$ (43,165,594)	$ (34,366,718)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	211,391	206,794
Loss on disposal of property and equipment		168
Non cash lease expense	459,599
Stock-based compensation expense	4,488,985	3,437,341
Changes in assets and liabilities
Prepaid expenses and other current assets	(1,642,917)	689,698
Prepaid research and development expenses		(1,510,607)
Accounts payable	(1,256,031)	(1,987,696)
Accrued expenses and bonuses	2,244,062	232,534
Operating lease liabilities	(530,818)	(52,644)
Net cash used in operating activities	(39,191,323)	(33,351,130)
Investing activities
Purchases of property and equipment	(132,571)	(68,614)
Net cash used in investing activities	(132,571)	(68,614)
Financing activities
Proceeds from issuance of common stock, net of issuance costs		128,425,080
Proceeds from exercise of stock options and warrants	293,091	898,560
Net cash provided by financing activities	293,091	129,323,640
Net change in cash and cash equivalents	(39,030,803)	95,903,896
Cash and cash equivalents, beginning of period	209,917,595	123,924,738
Cash and cash equivalents, end of period	$ 170,886,792	$ 219,828,634

Description of the Business

Description of the Business	9 Months Ended
	Sep. 30, 2019
Description of the Business
Description of the Business	GLYCOMIMETICS, INC. Notes to Unaudited Financial Statement 1. Description of the Business GlycoMimetics, Inc. (the Company), a Delaware corporation headquartered in Rockville, Maryland, was incorporated in April 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. Using its expertise in carbohydrate chemistry and knowledge of carbohydrate biology, the Company is developing a pipeline of proprietary glycomimetics that 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 may seek additional capital through arrangements with strategic partners or from other sources.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
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, 2019, statements of operations and comprehensive loss and statements of stockholders’ equity for the three and nine months ended September 30, 2019 and 2018 and statements of cash flows for the nine months ended September 30, 2019 and 2018 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, 2018 contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 6, 2019. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements, except for the effect of adopting ASU 2016-02 Leases ( Topic 842 ), as described below under “Recently Issued Accounting Standards—Adopted Accounting Standards,” 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, 2019, its results of operations for the three and nine months ended September 30, 2019 and 2018, changes in its stockholders’ equity for the three and nine months ended September 30, 2019 and 2018 and its cash flows for the nine months ended September 30, 2019 and 2018. The December 31, 2018 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, 2019 and 2018 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, 2019 and December 31, 2018. The carrying value of cash held in money market funds of $168.9 million and $207.9 million as of September 30, 2019 and December 31, 2018, 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 The Company applies Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers (Topic 606), 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. The Company enters into licensing agreements which are within the scope of Topic 606, under which it licenses certain of its drug 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, 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 under Topic 606 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 entered into a collaborative research and development agreement with Pfizer Inc. (Pfizer) in 2011. 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. Pfizer announced on August 2, 2019 that the licensed product candidate that was the subject of the Pfizer Agreement did not meet the primary or key secondary efficacy endpoints of the pivotal Phase 3 clinical trial being conducted by Pfizer. Pfizer’s analysis of the Phase 3 trial results is ongoing, and the Pfizer Agreement remains in effect, although the Company does not currently expect to receive any further milestone payments or royalties under the Pfizer Agreement. 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 Research and development costs are expensed as incurred. For payments made in advance, the Company defers the cost and 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. The following potentially dilutive securities outstanding, at September 30, 2019 and 2018, have been excluded from the computation of diluted weighted-average common shares outstanding, as they would be anti-dilutive: 2019 2018 Stock options and restricted stock units 5,241,838 3,976,362 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, 2019 and 2018, the Company’s net loss equaled comprehensive net loss and, accordingly, no additional disclosure is presented. Recently Issued Accounting Standards Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) issued ASU No. 2016-02, Leases (Topic 842) , which 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 No. 2016-02 were applied using a modified retrospective approach and were adopted by the Company effective January 1, 2019. The Company elected the transition option provided under ASU No. 2018-11, which did not require adjustments to comparative periods or modified disclosures in those comparative periods. The Company elected the practical expedient as an accounting policy election by class of underlying asset to account for each separate lease component of a contract and its associated non-lease component as a single lease component. This practical expedient was applied to all underlying asset classes. Upon adoption of the standard, the Company recorded right-of-use assets and related lease liabilities for operating leases of approximately $3.6 million and $4.3 million, respectively, as of January 1, 2019. The difference between these amounts is comprised of adjustments related to unamortized balances of deferred rent, lease incentives, and prepaid rent existing as of the effective date. The adoption of the standard did not materially affect the Company’s net earnings or the statement of cash flows. For further discussion on the adoption of this standard, see Note 6, “Leases.” 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 Company adopted this ASU as of January 1, 2019. Upon transition, the Company measured nonemployee awards at fair value as of the adoption date. The adoption of the standard did not materially affect the Company’s operating results, cash flows or financial position. In August 2018, the U.S. Securities and Exchange Commission (SEC) adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification. This final rule amends certain disclosure requirements that are redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expand the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. Effective with the adoption of the rule, the Company has included a separate statement of stockholders’ equity in the financial statements for the three and nine months ended September 30, 2019 and 2018. Accounting Standards Not Yet Adopted In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 . The amendment clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in Topic 606 should be applied, including recognition, measurement, presentation and disclosure requirements. The amendment also adds unit-of-account guidance in Topic 808 to align with the guidance in Topic 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of Topic 606. Lastly, the amendment requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under Topic 606 is precluded if the collaborative arrangement participant is not a customer. For public business entities, the amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company is currently evaluating these clarifications in the accounting and presentation for its collaborative arrangements within the scope of Topic 808 but does not expect it will have any material impact. 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 Curr

Prepaid Expenses and Other Current Assets	9 Months Ended
	Sep. 30, 2019
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, 2019 2018 Prepaid research and development expenses $ 2,921,151 $ 1,608,768 Other prepaid expenses 410,247 329,634 Other receivables 578,581 413,122 Prepaid expenses and other current assets $ 3,909,979 $ 2,351,524

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2019
Property and Equipment
Property and Equipment	4. Property and Equipment Property and equipment, net consists of the following: September 30, December 31, 2019 2018 Furniture and fixtures $ 345,712 $ 334,300 Laboratory equipment 1,402,436 1,389,036 Office equipment 11,085 11,085 Computer equipment 296,744 233,282 Leasehold improvements 616,132 573,165 Property and equipment 2,672,109 Less accumulated depreciation (1,793,703) (1,583,642) Property and equipment, net $ 878,406 $ 957,226 Depreciation expense was $70,783 and $68,477 for the three months ended September 30, 2019 and 2018, respectively, and $211,391 and $206,794 for the nine months ended September 30, 2019 and 2018, respectively.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2019
Accrued Expenses
Accrued Expenses	5. Accrued Expenses The following is a summary of the Company’s accrued expenses: September 30, December 31, 2019 2018 Accrued research and development expenses $ 5,732,775 $ 3,483,741 Accrued consulting and other professional fees 257,467 140,397 Accrued employee benefits 465,385 385,789 Other accrued expenses 143,620 263,693 Accrued expenses $ 6,599,247 $ 4,273,620

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Operating Leases
Operating leases	6. Leases At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the circumstances present. The Company determines a lease exists if the contract conveys the right to control an identified asset for a period of time in exchange for consideration. Control is considered to exist when the lessee has the right to obtain substantially all of the economic benefits from the use of an identified asset as well as direct the right to use of that asset. Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets, lease liabilities and, if applicable, long-term lease liabilities. The Company has elected not to recognize on the balance sheet leases with terms of one year or less on the lease commencement date. If a contract is considered to be a lease, the Company recognizes a lease liability based on the present value of the future lease payments over the expected lease term, with an offsetting entry to recognize a right-of-use asset. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company utilizes the appropriate incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a term similar to the term of the lease for which the rate is estimated. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. The Company leases office and research space in Rockville, Maryland under an operating lease with a term from June 15, 2015 through October 31, 2023 (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 in the initial year of the Lease. In March 2016, the Company amended the Lease (the Lease Amendment) to lease additional space as of June 1, 2016 . 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. The Company identified and applied the following significant assumptions in recognizing the right-of-use asset and corresponding liability for the Lease and Lease Amendment: · Lease term – The lease term includes both the noncancelable period and, when applicable, cancelable option periods where failure to exercise such option would result in an economic penalty. The Company’s renewal option to extend is not reasonably certain of being exercised as of September 30, 2019. · Incremental borrowing rate – As the Company’s lease does not provide an implicit rate, the Company used an incremental borrowing rate, or IBR, which is the rate incurred to borrow on a collateralized basis over a term similar to the term of the lease for which the rate is estimated. The Company determined the IBR based on an estimated rate that considered the Company’s credit risk in the United States for a collateralized borrowing and lease term similar to the Lease. With the adoption of ASU 2016-02 on January 1, 2019, the Company recorded a right-of use asset of $3.6 million and corresponding lease liability of $4.3 million by calculating the present value of lease payments, discounted at 8.01%, the Company’s IBR, over the expected term of 4.8 years. The Company has elected to use the practical expedient and account for each lease component and related non-lease component as one single component. The lease component results in a right-of-use asset being recorded on the balance sheet and amortized as lease expense on a straight-line basis. As of September 30, 2019 the weighted-average remaining lease term was 4.08 years. There were no additional operating leases entered into during the nine months ended September 30, 2019. The components of lease expense and related cash flows were as follows: Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Operating lease cost $ 231,989 $ 695,968 Variable lease cost 148,353 324,834 Total operating lease cost $ 380,342 $ 1,020,802 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 259,014 $ 767,894 Maturities of lease liability due under these lease agreements as of September 30, 2019 were as follows: Operating Lease Obligation October 1, 2019 - December 31, 2019 $ 259,722 2020 1,052,580 2021 1,078,895 2022 1,105,867 2023 846,825 Thereafter — Total 4,343,889 Present value adjustment (622,637) Present value of lease payments $ 3,721,252

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Stockholders' Equity
Disclosure of stockholders' equity and share-based compensation	7. Stockholders’ Equity 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, 2019, $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, 2019 or 2018. 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, 2019 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, 2018 667,080 $ 1.24 2.2 Options exercised (177,759) 1.12 Options forfeited — Outstanding, Vested and Exercisable as of September 30, 2019 489,321 1.29 1.5 $ 1,479 As of September 30, 2019, 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, 2019 and 2018 was $266,450 and $680,200, respectively, and total cash received for options exercised was $199,090 and $56,299 during the nine months ended September 30, 2019 and 2018, respectively. 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, 2019, the number of shares of common stock that may be issued under the 2013 Plan was automatically increased by 1,294,822 shares, representing 3% of the total number of shares of common stock outstanding on December 31, 2018, increasing the number of shares of common stock available for issuance under the 2013 Plan to 5,162,816 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, 2019 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, 2018 3,265,254 $ 8.39 7.1 Options granted 1,191,071 10.96 Options exercised (16,606) 5.66 Options forfeited (19,308) 13.79 Outstanding as of September 30, 2019 4,420,411 10.43 7.1 $ 2 Vested or expected to vest as of September 30, 2019 4,420,411 10.43 7.1 $ 2 Exercisable as of September 30, 2019 2,567,818 9.12 5.9 $ — The weighted-average fair value of the options granted during the nine months ended September 30, 2019 and 2018 was $7.17 per share and $13.11 per share, respectively, applying the Black-Scholes-Merton option pricing model utilizing the following weighted-average assumptions: Nine Months Ended September 30, 2019 2018 Expected term 6.25 years 6.25 years Expected volatility 71.15% 73.83% Risk-free interest rate 2.54% 2.53% Expected dividend yield 0% 0% As of September 30, 2019, there was $13,050,347 of total unrecognized compensation expense related to unvested options under the 2013 Plan that will be recognized over a weighted-average period of approximately 2.7 years. Total intrinsic value of the options exercised during the nine months ended September 30, 2019 and 2018 was $97,429 and $1,243,400, respectively, and total cash received for options exercised was $94,001 and $839,924 during the nine months ended September 30, 2019 and 2018, respectively. The total fair value of shares underlying options which vested in the nine months ended September 30, 2019 and 2018 was $5,296,451 and $2,611,141, 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. In September 2019, the Company granted an aggregate of 332,106 RSUs with service conditions to the Company’s non-executive employees. The RSUs granted in September 2019 vest over a two-year period, with one-third vesting on the first anniversary of the date of grant and the remaining two-thirds vesting on the second anniversary of the date of grant, provided that the employee remains employed with the Company at the applicable vesting date. As of September 30, 2019, there was $1,477,649 of total unrecognized compensation expense associated with these RSU grants that will be recognized over a weighted-average period of approximately two years. The following is a summary of RSU activity under the 2013 Plan for the nine months ended September 30, 2019: Weighted-Average Number of Shares Grant Date Underlying RSUs Fair Value Unvested at December 31, 2018 4,833 $ 4.61 Granted 332,106 4.53 Forfeited — — Vested (4,833) 4.61 Unvested at September 30, 2019 332,106 4.53 Stock-based compensation expense was classified on the statements of operations as follows for the three and nine months ended September 30, 2019 and 2018: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development expense $ 610,506 $ 429,477 $ 1,697,171 $ 1,282,040 General and administrative expense 976,641 741,646 2,791,814 2,155,301 Total stock-based compensation expense $ 1,587,147 $ 1,171,123 $ 4,488,985 $ 3,437,341

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Taxes
Income Taxes	8. Income Taxes The Company has not recorded any tax provision or benefit for the nine months ended September 30, 2019 and 2018. 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, 2019 and December 31, 2018.

Research and License Agreements

Research and License Agreements	9 Months Ended
	Sep. 30, 2019
Research And License Agreements [Abstract]
Research and License Agreement	9. Research and License Agreements In 2011, the Company and Pfizer entered into the Pfizer Agreement, which provides Pfizer an exclusive worldwide license to rivipansel for vaso-occlusive crisis associated with sickle cell disease (SCD) and for other diseases for which the drug candidate may be developed. On August 2, 2019, Pfizer announced that the pivotal Phase 3 clinical trial to evaluate the efficacy and safety of rivipansel did not meet its primary or key secondary efficacy endpoints. Pfizer’s analysis of the Phase 3 results is ongoing, and the Pfizer Agreement remains in effect, although the Company does not currently expect to receive any of the potential future milestone payments described below. Under the Pfizer Agreement, the Company was responsible for completion of the Phase 2 clinical trial of rivipansel, 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. With respect to rivipansel for the treatment of SCD, the Pfizer Agreement provides for potential development, regulatory and commercial milestone payments of up to $120.0 million in the aggregate, and for any additional indication that may be developed by Pfizer, the Pfizer Agreement provides for potential development, commercial and regulatory milestone payments of up to $65.0 million in the aggregate. The Pfizer Agreement also provides for 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. 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 SCD 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. Based on the Company’s assessment, the Company determined that the rivipansel license and R&D services are not distinct and are therefore considered as one combined performance obligation. 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 the 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. The transaction price of the up-front fee is equal to the $22.5 million received. The fixed up-front consideration was recognized under ASC 606 based on when control of the combined performance obligation was transferred to the customer, which corresponded 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. Future event-driven milestones will be recognized when the constraint no longer applies. The Company received a $15.0 million non-refundable milestone payment in May 2014 and an additional non-refundable milestone payment of $20.0 million in June 2015. The Company did not recognize any revenue under the Pfizer Agreement during the nine months ended September 30, 2019 or 2018. 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 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, 2019 or 2018.

Summary of Significant Accounti

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Summary of Significant Accounting Policies
Basis of Accounting	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	Unaudited Financial Statements The accompanying balance sheet as of September 30, 2019, statements of operations and comprehensive loss and statements of stockholders’ equity for the three and nine months ended September 30, 2019 and 2018 and statements of cash flows for the nine months ended September 30, 2019 and 2018 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, 2018 contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 6, 2019. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements, except for the effect of adopting ASU 2016-02 Leases ( Topic 842 ), as described below under “Recently Issued Accounting Standards—Adopted Accounting Standards,” 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, 2019, its results of operations for the three and nine months ended September 30, 2019 and 2018, changes in its stockholders’ equity for the three and nine months ended September 30, 2019 and 2018 and its cash flows for the nine months ended September 30, 2019 and 2018. The December 31, 2018 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, 2019 and 2018 are unaudited. Interim results are not necessarily indicative of results for an entire year or for any future period.
Use of Estimates	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	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, 2019 and December 31, 2018. The carrying value of cash held in money market funds of $168.9 million and $207.9 million as of September 30, 2019 and December 31, 2018, respectively, is included in cash and cash equivalents and approximates market values based on quoted market prices (Level 1 inputs).
Concentration of Credit Risk	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	Revenue Recognition The Company applies Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers (Topic 606), 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. The Company enters into licensing agreements which are within the scope of Topic 606, under which it licenses certain of its drug 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, 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 under Topic 606 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 entered into a collaborative research and development agreement with Pfizer Inc. (Pfizer) in 2011. 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. Pfizer announced on August 2, 2019 that the licensed product candidate that was the subject of the Pfizer Agreement did not meet the primary or key secondary efficacy endpoints of the pivotal Phase 3 clinical trial being conducted by Pfizer. Pfizer’s analysis of the Phase 3 trial results is ongoing, and the Pfizer Agreement remains in effect, although the Company does not currently expect to receive any further milestone payments or royalties under the Pfizer Agreement. For a complete discussion of the Company’s accounting for the Pfizer Agreement, see Note 9, “Research and License Agreements.”
Accrued Liabilities	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	Research and Development Costs Research and development costs are expensed as incurred. For payments made in advance, the Company defers the cost and 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 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	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. The following potentially dilutive securities outstanding, at September 30, 2019 and 2018, have been excluded from the computation of diluted weighted-average common shares outstanding, as they would be anti-dilutive: 2019 2018 Stock options and restricted stock units 5,241,838 3,976,362
Comprehensive Loss	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, 2019 and 2018, the Company’s net loss equaled comprehensive net loss and, accordingly, no additional disclosure is presented.
Adopted Accounting Standards	Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (FASB) issued ASU No. 2016-02, Leases (Topic 842) , which 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 No. 2016-02 were applied using a modified retrospective approach and were adopted by the Company effective January 1, 2019. The Company elected the transition option provided under ASU No. 2018-11, which did not require adjustments to comparative periods or modified disclosures in those comparative periods. The Company elected the practical expedient as an accounting policy election by class of underlying asset to account for each separate lease component of a contract and its associated non-lease component as a single lease component. This practical expedient was applied to all underlying asset classes. Upon adoption of the standard, the Company recorded right-of-use assets and related lease liabilities for operating leases of approximately $3.6 million and $4.3 million, respectively, as of January 1, 2019. The difference between these amounts is comprised of adjustments related to unamortized balances of deferred rent, lease incentives, and prepaid rent existing as of the effective date. The adoption of the standard did not materially affect the Company’s net earnings or the statement of cash flows. For further discussion on the adoption of this standard, see Note 6, “Leases.” 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 Company adopted this ASU as of January 1, 2019. Upon transition, the Company measured nonemployee awards at fair value as of the adoption date. The adoption of the standard did not materially affect the Company’s operating results, cash flows or financial position. In August 2018, the U.S. Securities and Exchange Commission (SEC) adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification. This final rule amends certain disclosure requirements that are redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expand the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. Effective with the adoption of the rule, the Company has included a separate statement of stockholders’ equity in the financial statements for the three and nine months ended September 30, 2019 and 2018.
Accounting Standards Not Yet Adopted	Accounting Standards Not Yet Adopted In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 . The amendment clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in Topic 606 should be applied, including recognition, measurement, presentation and disclosure requirements. The amendment also adds unit-of-account guidance in Topic 808 to align with the guidance in Topic 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of Topic 606. Lastly, the amendment requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under Topic 606 is precluded if the collaborative arrangement participant is not a customer. For public business entities, the amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company is currently evaluating these clarifications in the accounting and presentation for its collaborative arrangements within the scope of Topic 808 but does not expect it will have any material impact. 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.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Summary of Significant Accounting Policies
Potentially dilutive securities outstanding	2019 2018 Stock options and restricted stock units 5,241,838 3,976,362

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	9 Months Ended
	Sep. 30, 2019
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, 2019 2018 Prepaid research and development expenses $ 2,921,151 $ 1,608,768 Other prepaid expenses 410,247 329,634 Other receivables 578,581 413,122 Prepaid expenses and other current assets $ 3,909,979 $ 2,351,524

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2019
Property and Equipment
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: September 30, December 31, 2019 2018 Furniture and fixtures $ 345,712 $ 334,300 Laboratory equipment 1,402,436 1,389,036 Office equipment 11,085 11,085 Computer equipment 296,744 233,282 Leasehold improvements 616,132 573,165 Property and equipment 2,672,109 Less accumulated depreciation (1,793,703) (1,583,642) Property and equipment, net $ 878,406 $ 957,226

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2019
Accrued Expenses
Summary of Accrued Expenses	September 30, December 31, 2019 2018 Accrued research and development expenses $ 5,732,775 $ 3,483,741 Accrued consulting and other professional fees 257,467 140,397 Accrued employee benefits 465,385 385,789 Other accrued expenses 143,620 263,693 Accrued expenses $ 6,599,247 $ 4,273,620

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Operating Leases
Components of lease expense and related cash flows	Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Operating lease cost $ 231,989 $ 695,968 Variable lease cost 148,353 324,834 Total operating lease cost $ 380,342 $ 1,020,802 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 259,014 $ 767,894
Maturities of lease liabilities due	Operating Lease Obligation October 1, 2019 - December 31, 2019 $ 259,722 2020 1,052,580 2021 1,078,895 2022 1,105,867 2023 846,825 Thereafter — Total 4,343,889 Present value adjustment (622,637) Present value of lease payments $ 3,721,252

Stockholders Equity (Tables)

Stockholders Equity (Tables)	9 Months Ended
	Sep. 30, 2019
Stock-Based Compensation Expense	Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development expense $ 610,506 $ 429,477 $ 1,697,171 $ 1,282,040 General and administrative expense 976,641 741,646 2,791,814 2,155,301 Total stock-based compensation expense $ 1,587,147 $ 1,171,123 $ 4,488,985 $ 3,437,341
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, 2019 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, 2018 667,080 $ 1.24 2.2 Options exercised (177,759) 1.12 Options forfeited — Outstanding, Vested and Exercisable as of September 30, 2019 489,321 1.29 1.5 $ 1,479
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, 2019 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, 2018 3,265,254 $ 8.39 7.1 Options granted 1,191,071 10.96 Options exercised (16,606) 5.66 Options forfeited (19,308) 13.79 Outstanding as of September 30, 2019 4,420,411 10.43 7.1 $ 2 Vested or expected to vest as of September 30, 2019 4,420,411 10.43 7.1 $ 2 Exercisable as of September 30, 2019 2,567,818 9.12 5.9 $ —
Weighted-Average Fair Value of Options Granted	Nine Months Ended September 30, 2019 2018 Expected term 6.25 years 6.25 years Expected volatility 71.15% 73.83% Risk-free interest rate 2.54% 2.53% 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, 2019: Weighted-Average Number of Shares Grant Date Underlying RSUs Fair Value Unvested at December 31, 2018 4,833 $ 4.61 Granted 332,106 4.53 Forfeited — — Vested (4,833) 4.61 Unvested at September 30, 2019 332,106 4.53

Significant Accounting Polici_2

Significant Accounting Policies (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Mar. 31, 2018
Share-based Compensation
Expected term	6 years 3 months	6 years 3 months
Level 1
Fair Value Measurements
Carrying value of cash held in money market fund	$ 168.9		$ 207.9
Level 2
Fair Value Measurements
Assets measured at fair value levels 2 or 3	0		0
Liabilities measured at fair value levels 2 or 3	0		0
Level 3
Fair Value Measurements
Assets measured at fair value levels 2 or 3	0		$ 0
Liabilities measured at fair value levels 2 or 3	$ 0			$ 0
Maximum
Share-based Compensation
Expiration period	10 years

Significant Accounting Polici_3

Significant Accounting Policies - Net Loss Per Common Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Stock options and restricted stock units
Anti-dilutive securities excluded
Anti-dilutive securities	5,241,838	3,976,362

Significant Accounting Polici_4

Significant Accounting Policies - Recently Issued Accounting Standards (Details) - USD ($)	Jan. 01, 2019	Sep. 30, 2019
New accounting pronouncement, modified retrospective method
Operating Lease, Right-of-Use Asset	$ 3,600,000	$ 3,166,539
Operating Lease, Liability	$ 4,300,000	$ 3,721,252
ASU 2016-02
New accounting pronouncement, modified retrospective method
Accounting principle adopted	true
Transition option upon adoption	Modified Retrospective
Prior periods not restated	true
Operating Lease, Right-of-Use Asset	$ 3,600,000
Operating Lease, Liability	$ 4,300,000
ASU 2018-07
New accounting pronouncement, modified retrospective method
Accounting principle adopted	true

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Prepaid Expenses and Other Current Assets
Prepaid research and development expenses	$ 2,921,151	$ 1,608,768
Other prepaid expenses	410,247	329,634
Other receivables	578,581	413,122
Prepaid expenses and other current assets	$ 3,909,979	$ 2,351,524

Property and Equipment (Details

Property and Equipment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,672,109		$ 2,672,109		$ 2,540,868
Less accumulated depreciation	(1,793,703)		(1,793,703)		(1,583,642)
Property and equipment, net	878,406		878,406		957,226
Depreciation of property and equipment	70,783	$ 68,477	211,391	$ 206,794
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	345,712		345,712		334,300
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	1,402,436		1,402,436		1,389,036
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	296,744		296,744		233,282
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 616,132		$ 616,132		$ 573,165

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Accrued Expenses
Accrued research and development expenses	$ 5,732,775	$ 3,483,741
Accrued consulting and other professional fees	257,467	140,397
Accrued employee benefits	465,385	385,789
Other accrued expenses	143,620	263,693
Accrued expenses	$ 6,599,247	$ 4,273,620

Leases (Details)

Leases (Details)	9 Months Ended
	Sep. 30, 2019USD ($)lease	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	May 31, 2016USD ($)
Operating leases
Security Deposit	$ 52,320		$ 52,320
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Lessee, Operating Lease, Existence of Option to Terminate [true false]	true
Operating Lease, Right-of-Use Asset	$ 3,166,539	$ 3,600,000
Operating Lease, Liability	$ 3,721,252	$ 4,300,000
Lessee, Operating Lease, Discount Rate		8.01%
Operating Lease, Weighted Average Remaining Lease Term	4 years 29 days	4 years 9 months 18 days
Number of additional operating leases entered during the period | lease	0
Rockville Maryland
Operating leases
Security Deposit				$ 52,320

Leases - Components of lease ex

Leases - Components of lease expense (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Components of lease expense
Operating lease cost	$ 231,989	$ 695,968
Variable lease cost	148,353	324,834
Total operating lease cost	380,342	1,020,802
Related cash flows
Operating cash flows from operating leases	$ 259,014	$ 767,894

Leases - Maturities of lease li

Leases - Maturities of lease liability (Details) - USD ($)	Sep. 30, 2019	Jan. 01, 2019
Maturities of lease liability due
October 1, 2019 - December 31, 2019	$ 259,722
2020	1,052,580
2021	1,078,895
2022	1,105,867
2023	846,825
Thereafter
Total	4,343,889
Present value adjustment	(622,637)
Present value of lease payments	$ 3,721,252	$ 4,300,000

Stockholders' Equity - Equity O

Stockholders' Equity - Equity Offerings (Details) - September 2017 At-The-Market - Common Stock - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 28, 2017
Equity offerings
Common stock available for sale under agreement	$ 80
Securities sold during period	0	0
Maximum
Equity offerings
Common stock available for sale under agreement			$ 100

Stockholders' Equity - Incentiv

Stockholders' Equity - Incentive Plans (Details) - USD ($)	Jan. 01, 2019	Jan. 09, 2014	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
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				$ 266,450	$ 680,200
Cash proceeds from exercise of stock options				$ 199,090	56,299
Options exercised				177,759
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			$ 13,050,347	$ 13,050,347
Period for unrecognized compensation expense related to unvested options yet has not been recognized				2 years 8 months 12 days
Intrinsic value of options exercised				$ 97,429	1,243,400
Cash proceeds from exercise of stock options				$ 94,001	839,924
Options exercised				16,606
Fair value of shares vested				$ 5,296,451	$ 2,611,141
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
Incentive plans
Options exercised			166,759	199,198
Common Stock | 2013 Equity Incentive Plan
Authorized shares
Common stock authorized under 2013 plan	5,162,816	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	1,294,822

Stockholders' Equity - Company'

Stockholders' Equity - Company's Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2018$ / sharesshares
2003 Stock Incentive Plan
OUTSTANDING OPTIONS
Outstanding at beginning of period | shares	667,080
Options exercised | shares	(177,759)
Outstanding at end of period | shares	489,321	667,080
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period | $ / shares	$ 1.24
Options exercised | $ / shares	1.12
Outstanding at end of period | $ / shares	$ 1.29	$ 1.24
VESTED AND EXPECTED TO VEST
Outstanding options | shares	489,321
Weighted-Average Exercise Price | $ / shares	$ 1.29
Aggregate Intrinsic Value (in thousands) | $	$ 1,479
ADDITIONAL DISCLOSURES
Outstanding options exercisable at end of period | shares	489,321
Weighted-average exercise price exercisable at end of period | $ / shares	$ 1.29
Weighted-average contractual term (years) exercisable at end of period	1 year 6 months
Aggregate intrinsic value (in thousands) exercisable at end of period | $	$ 1,479
Weighted-average contractual term outstanding	1 year 6 months	2 years 2 months 12 days
Aggregate intrinsic value (in thousands) outstanding at end of period | $	$ 1,479
2013 Equity Incentive Plan
OUTSTANDING OPTIONS
Outstanding at beginning of period | shares	3,265,254
Options granted | shares	1,191,071
Options exercised | shares	(16,606)
Options forfeited | shares	(19,308)
Outstanding at end of period | shares	4,420,411	3,265,254
WEIGHTED-AVERAGE EXERCISE PRICE
Outstanding at beginning of period | $ / shares	$ 8.39
Options granted | $ / shares	10.96
Options exercised | $ / shares	5.66
Options forfeited | $ / shares	13.79
Outstanding at end of period | $ / shares	$ 10.43	$ 8.39
VESTED AND EXPECTED TO VEST
Outstanding options | shares	4,420,411
Weighted-Average Exercise Price | $ / shares	$ 10.43
Weighted-Average Remaining Contractual Term	7 years 1 month 6 days
Aggregate Intrinsic Value (in thousands) | $	$ 2
ADDITIONAL DISCLOSURES
Outstanding options exercisable at end of period | shares	2,567,818
Weighted-average exercise price exercisable at end of period | $ / shares	$ 9.12
Weighted-average contractual term (years) exercisable at end of period	5 years 10 months 24 days
Weighted-average contractual term outstanding	7 years 1 month 6 days	7 years 1 month 6 days
Aggregate intrinsic value (in thousands) outstanding at end of period | $	$ 2

Stockholders' Equity - Weighted

Stockholders' Equity - Weighted-Average assumptions (Details) - $ / shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Weighted-average assumptions
Expected term	6 years 3 months	6 years 3 months
Expected volatility	71.15%	73.83%
Risk-free interest rate	2.54%	2.53%
Expected dividend yield	0.00%	0.00%
2013 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value of the options granted	$ 7.17	$ 13.11

Stockholders' Equity - Summary

Stockholders' Equity - Summary of RSU Activity (Details) - 2013 Equity Incentive Plan - USD ($)	Jan. 09, 2014	Sep. 30, 2019	Sep. 30, 2019
Restricted Stock Units information
Period for unrecognized compensation expense related to unvested options yet has not been recognized			2 years 8 months 12 days
Upon first anniversary of start date
Restricted Stock Units information
Percent of shares subject to option grant that will vest	25.00%
RSU [Member]
NUMBER OF SHARES
Unvested at beginning of period			4,833
Granted			332,106
Forfeited			0
Vested			(4,833)
Unvested at end of period		332,106	332,106
WEIGHTED-AVERAGE GRANT DATE FAIR VALUE
Unvested at beginning of period			$ 4.61
Granted			4.53
Forfeited			0
Vested			4.61
Unvested at end of period		$ 4.53	$ 4.53
RSU [Member] | Non-executive employees
Restricted Stock Units information
Vesting period		2 years
Unrecognized compensation expense related to unvested service RSUs		$ 1,477,649	$ 1,477,649
Period for unrecognized compensation expense related to unvested options yet has not been recognized			2 years
NUMBER OF SHARES
Granted		332,106
RSU [Member] | Non-executive employees | Upon first anniversary of start date
Restricted Stock Units information
Percent of shares subject to option grant that will vest		33.30%
RSU [Member] | Non-executive employees | On the second anniversary of the date of grant
Restricted Stock Units information
Percent of shares subject to option grant that will vest		66.70%

Stockholders' Equity - Stock-Ba

Stockholders' Equity - Stock-Based Compensation Expense (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock-based compensation expense
Total stock-based compensation expense	$ 1,587,147	$ 1,171,123	$ 4,488,985	$ 3,437,341
Research and Development
Stock-based compensation expense
Total stock-based compensation expense	610,506	429,477	1,697,171	1,282,040
General and Administrative Expense.
Stock-based compensation expense
Total stock-based compensation expense	$ 976,641	$ 741,646	$ 2,791,814	$ 2,155,301

Income Taxes (Details)

Income Taxes (Details) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Income Taxes
Income tax (benefit) provision	$ 0	$ 0

Research and License Agreemen_2

Research and License Agreements - Additional Information (Details)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2015USD ($)	May 31, 2014USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)item	Sep. 30, 2018USD ($)	Dec. 31, 2011USD ($)
Research and License Agreements
Non-refundable milestone payment received	$ 20,000,000	$ 15,000,000
Revenue
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 Development Regulatory And Commercial Milestones [Member] | License Agreement | Rivipansel [Member] | Pfizer | Maximum
Research and License Agreements
Potential milestone payments							120,000,000
Achievement Of Development Regulatory And Commercial Milestones [Member] | License Agreement | Additional Indications [Member] | Pfizer | Maximum
Research and License Agreements
Potential milestone payments							65,000,000
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