October 13, 2023

VIA EDGAR AND OVERNIGHT COURIER

Office of Life Sciences

Division of Corporation Finance

Securities and Exchange Commission

100 F Street, N.E.

Washington, D.C. 20549

Attention: Cindy Polynice

Joe McCann

Tracie Mariner

Angela Connell

Ladies and Gentlemen:

This letter is submitted on behalf of FibroBiologics, Inc. (the “Company”) in response to comments of the staff (the “Staff”) of the U.S. Securities and Exchange Commission (the “Commission”) with respect to the Company’s Amendment No. 1 to Draft Registration Statement on Form S-1 confidentially submitted on August 16, 2023 (the “Draft Registration Statement”), as set forth in the Staff’s letter dated September 11, 2023 (the “Comment Letter”).

Set forth below are the Company’s responses to the Staff’s comments in the Comment Letter. For reference purposes, the text of the Staff’s comments are reproduced in bold below, followed by the Company’s response to the comment. The numbered paragraphs below correspond to the numbered comments in the Comment Letter.

Additionally, the Company is concurrently confidentially submitting Amendment No. 2 to the Draft Registration Statement (“Amendment No. 2”), which reflects revisions in response to the Comment Letter and certain other updates. For the convenience of the Staff, we are also sending, by overnight courier, copies of this letter and copies of Amendment No. 2, marked to show changes to the Draft Registration Statement as originally confidentially submitted.

Cover Page

Company Response: In response to the Staff’s comment, the Company has revised the referenced disclosure on the cover page of Amendment No. 2 to disclose that Series B Preferred Stock and the Series B-1 Preferred Stock will automatically convert, without the payment of additional consideration by or to the holder thereof, into shares of common stock on a one-for-one basis upon the Direct Listing (as defined in Amendment No. 2).

Our Current Pipeline, page 3

Company Response: In response to the Staff’s comment, the Company has revised the pipeline chart on pages 3 and 79 of Amendment No. 2, by aligning each column header with its respective column, to clarify the present status for each of its product candidates set forth therein.

Management’s Discussion and Analysis of Financial Condition and Results of Operations

Critical Accounting Estimates

Stock-Based Compensation, page 76

Company Response: In response to the Staff’s comment, the Company has expanded its disclosure in Amendment No. 2 to state that the estimated fair value of its common stock used to determine stock-based compensation expense will not be necessary to determine the fair value of new awards once the underlying shares begin trading.

Our Solution, page 82

Company Response: In response to the Staff’s comment, the Company has revised the referenced disclosure in Amendment No. 2 to identify the safety and efficacy endpoints for the planned Phase 1/2 trial for CybroCell.

Principal and Registered Stockholders, page 114

Company Response: In response to the Staff’s comment, the Company has revised the referenced disclosure in Amendment No. 2 to explain how many of the shares of common stock that will be outstanding upon the Direct Listing for principal and Registered Stockholders (as defined in Amendment No. 2) are attributable to the automatic conversion of (i) the non-voting common stock, (ii) the Series B Preferred Stock, and (iii) the Series B-1 Preferred Stock.

The Series A Preferred Stock, all of which are held by SpinalCyte LLC/FibroGenesis, will be automatically eliminated/cancelled, without the payment of additional consideration by or to the holder thereof, upon the Direct Listing, in accordance with the terms of the ROFN Agreement (as defined in Amendment No. 2). Other than the Series A Preferred Stock, all of which will be eliminated/cancelled as aforesaid, SpinalCyte LLC/FibroGenesis does not own any other shares of the Company’s capital stock. The Company has revised the disclosure under the section titled “Principal and Registered Stockholders” to state the foregoing.

Financial Statements

Note 7- Share Subscription Agreement, page F-11

Company Response:

The derivative resulting from the Share Purchase Agreement (as defined in Amendment No. 2) is effectively a put option to issue shares at a 10% discount. In determining a fair value of $0 for this derivative, the Company considered that (i) no shares have been sold and there is no obligation to sell shares in the future under this agreement so the up-front transaction price associated with the Share Purchase Agreement is $0 and equal to the fair value of the derivative and (ii) the derivative may reasonably be determined to have $0 fair value because a discount would likely be required by a market participant to purchase a large number of shares in the future.

The Company considered the probability of the commitment fee as part of its accounting for the Share Purchase Agreement but does not consider public listing to be “probable” until it occurs due to the uncertainty that remains even after a registration statement has been filed. This conclusion is consistent with the guidance found in Section 3.3.3.1 of PWC Viewpoint on Stock-Based Compensation, which states “[b]ecause an initial public offering is not probable until it occurs (i.e., until the offering closes), liability accounting would begin on the date of the initial public offering.”

The Company has obtained the requisite consent and has included the Share Purchase Agreement as an Exhibit to Amendment No. 2.

Remainder of page intentionally blank. Signature page follows.

Should the Staff have additional questions or comments regarding this submission, please do not hesitate to contact the undersigned at (713) 651-5557 or brian.fenske@nortonrosefulbright.com.

Enclosure

Mark Andersen, Chief Financial Officer

FibroBiologics, Inc.

Kelvin Kesse

Norton Rose Fulbright US LLP