Commitments and Contingencies	12 Months Ended
Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitments and Contingencies Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters arising out of the relationship between such parties and the Company. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations as of December 31, 2023 or 2022. Legal Proceedings On April 28, 2023, a class action complaint was filed in the United States District Court for the District of New Jersey against the Company and current and former officers (the “Securities Action”). On May 19, 2023, the Securities Action was transferred to the United States District Court for the District of Massachusetts, captioned Celano v. Fulcrum Therapeutics, Inc., et al., Case No. 1:23-cv-11125-IT. On July 31, 2023, the court appointed a lead plaintiff, who filed an amended complaint on September 29, 2023. The Securities Action alleges violations of Section 10(b) of the Securities Exchange Act of 1934, as amended, and Rule 10b-5 promulgated thereunder against all defendants and control person violations of Section 20(a) against the individuals, related to the Company’s February 2023 announcement that the U.S. Food and Drug Administration issued a clinical hold regarding the investigational new drug application for pociredir (formerly known as FTX-6058) for the potential treatment of sickle cell disease. The Securities Action alleges that the defendants made misleading statements and omitted to disclose material information related to the clinical hold and seeks, among other things, compensatory damages in connection with an allegedly inflated stock price between March 3, 2022, and March 8, 2023, as well as attorneys’ fees and costs. On November 28, 2023, all defendants filed a motion to dismiss the Securities Action, which motion is currently pending. The Company intends to defend vigorously against this litigation. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses the costs related to its legal proceedings as they are incurred. Other than attorneys’ fees and costs related to the defense of the Securities Action, no such costs have been incurred during the year ended December 31, 2023.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

13. Commitments and Contingencies

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters arising out of the relationship between such parties and the Company. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations as of December 31, 2023 or 2022.

Legal Proceedings

On April 28, 2023, a class action complaint was filed in the United States District Court for the District of New Jersey against the Company and current and former officers (the “Securities Action”). On May 19, 2023, the Securities Action was transferred to the United States District Court for the District of Massachusetts, captioned Celano v. Fulcrum Therapeutics, Inc., et al., Case No. 1:23-cv-11125-IT. On July 31, 2023, the court appointed a lead plaintiff, who filed an amended complaint on September 29, 2023. The Securities Action alleges violations of Section 10(b) of the Securities Exchange Act of 1934, as amended, and Rule 10b-5 promulgated thereunder against all defendants and control person violations of Section 20(a) against the individuals, related to the Company’s February 2023 announcement that the U.S. Food and Drug Administration issued a clinical hold regarding the investigational new drug application for pociredir (formerly known as FTX-6058) for the potential treatment of sickle cell disease. The Securities Action alleges that the defendants made misleading statements and omitted to disclose material information related to the clinical hold and seeks, among other things, compensatory damages in connection with an allegedly inflated stock price between March 3, 2022, and March 8, 2023, as well as attorneys’ fees and costs. On November 28, 2023, all defendants filed a motion to dismiss the Securities Action, which motion is currently pending. The Company intends to defend vigorously against this litigation.

At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses the costs related to its legal proceedings as they are incurred. Other than attorneys’ fees and costs related to the defense of the Securities Action, no such costs have been incurred during the year ended December 31, 2023.