0000001 - Document - Cover Page link:presentationLink link:calculationLink link:definitionLink 9952151 - Statement - Unaudited Condensed Consolidated Balance Sheets link:presentationLink link:calculationLink link:definitionLink 9952152 - Statement - Unaudited Condensed Consolidated Balance Sheets (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952153 - Statement - Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss link:presentationLink link:calculationLink link:definitionLink 9952154 - Statement - Unaudited Condensed Consolidated Statements of Stockholders’ (Deficit) Equity link:presentationLink link:calculationLink link:definitionLink 9952155 - Statement - Unaudited Condensed Consolidated Statements of Cash Flows link:presentationLink link:calculationLink link:definitionLink 9952156 - Disclosure - Basis of Presentation and Accounting Policies link:presentationLink link:calculationLink link:definitionLink 9952157 - Disclosure - Fair Value Measurements link:presentationLink link:calculationLink link:definitionLink 9952158 - Disclosure - Other Balance Sheet Components link:presentationLink link:calculationLink link:definitionLink 9952159 - Disclosure - Commitments and Contingencies link:presentationLink link:calculationLink link:definitionLink 9952160 - Disclosure - Collaboration and License Agreements link:presentationLink link:calculationLink link:definitionLink 9952161 - Disclosure - Derivative Tranche Liability link:presentationLink link:calculationLink link:definitionLink 9952162 - Disclosure - Stockholders’ Equity link:presentationLink link:calculationLink link:definitionLink 9952163 - Disclosure - Stock-Based Compensation link:presentationLink link:calculationLink link:definitionLink 9952164 - Disclosure - Income Taxes link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - Segment Reporting link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - Net Loss Per Share Attributable to Common Stockholders link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - Related Parties link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink 9955511 - Disclosure - Basis of Presentation and Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 9955512 - Disclosure - Basis of Presentation and Accounting Policies (Tables) link:presentationLink link:calculationLink link:definitionLink 9955513 - Disclosure - Fair Value Measurements (Tables) link:presentationLink link:calculationLink link:definitionLink 9955514 - Disclosure - Other Balance Sheet Components (Tables) link:presentationLink link:calculationLink link:definitionLink 9955515 - Disclosure - Commitments and Contingencies (Tables) link:presentationLink link:calculationLink link:definitionLink 9955516 - Disclosure - Stock-Based Compensation (Tables) link:presentationLink link:calculationLink link:definitionLink 9955517 - Disclosure - Segment Reporting (Tables) link:presentationLink link:calculationLink link:definitionLink 9955518 - Disclosure - Net Loss Per Share Attributable to Common Stockholders (Tables) link:presentationLink link:calculationLink link:definitionLink 9955519 - Disclosure - Basis of Presentation and Accounting Policies - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955520 - Disclosure - Basis of Presentation and Accounting Policies - Schedule of Cash and Cash Equivalents (Details) link:presentationLink link:calculationLink link:definitionLink 9955521 - Disclosure - Fair Value Measurements - Schedule of Financial Instruments Carried at Fair Value on a Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 9955522 - Disclosure - Fair Value Measurements - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955523 - Disclosure - Fair Value Measurements - Schedule of Fair Value, Liabilities Measured on Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 9955524 - Disclosure - Fair Value Measurements - Schedule of Fair Value Roll-forward of the Aggregate Fair Value of Derivative Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 9955525 - Disclosure - Other Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9955526 - Disclosure - Other Balance Sheet Components - Schedule of Property and Equipment, Net (Details) link:presentationLink link:calculationLink link:definitionLink 9955527 - Disclosure - Other Balance Sheet Components - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955528 - Disclosure - Other Balance Sheet Components - Schedule of Accrued Expenses and Other Current Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - Disclosure - Commitments and Contingencies - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955530 - Disclosure - Commitments and Contingencies - Schedule of Operating Lease Costs (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - Commitments and Contingencies - Schedule of Weighted Average Remaining Lease Term and Discount Rate of Operating Leases (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 9955533 - Disclosure - Collaboration and License Agreements - Children's Medical Center Corporation (Details) link:presentationLink link:calculationLink link:definitionLink 9955534 - Disclosure - Collaboration and License Agreements - Whitehead Institute for Biomedical Research (Details) link:presentationLink link:calculationLink link:definitionLink 9955535 - Disclosure - Collaboration and License Agreements - Fulcrum Therapeutics, Inc (Details) link:presentationLink link:calculationLink link:definitionLink 9955536 - Disclosure - Collaboration and License Agreements - BioMarin Pharmaceutical Inc (Details) link:presentationLink link:calculationLink link:definitionLink 9955537 - Disclosure - Collaboration and License Agreements - GlaxoSmithKline Intellectual Property (No. 3) Limited (“GSK”) (Details) link:presentationLink link:calculationLink link:definitionLink 9955538 - Disclosure - Derivative Tranche Liability (Details) link:presentationLink link:calculationLink link:definitionLink 9955539 - Disclosure - Stockholders’ Equity - Common and Preferred Stock Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955540 - Disclosure - Stockholders’ Equity - Recent Equity Financings Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955541 - Disclosure - Stockholders’ Equity - At-the-Market Sales Agreement Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955542 - Disclosure - Stock-Based Compensation - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955543 - Disclosure - Stock-Based Compensation - Schedule of Stock Options Fair Value Assumptions (Details) link:presentationLink link:calculationLink link:definitionLink 9955544 - Disclosure - Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955544 - Disclosure - Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955545 - Disclosure - Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 9955546 - Disclosure - Segment Reporting (Details) link:presentationLink link:calculationLink link:definitionLink 9955547 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss per Share (Details) link:presentationLink link:calculationLink link:definitionLink 9955548 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Schedule of Excluded Anti-dilutive Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9955549 - Disclosure - Related Parties (Details) link:presentationLink link:calculationLink link:definitionLink 9955550 - Disclosure - Subsequent Events (Details) link:presentationLink link:calculationLink link:definitionLink