The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F COVER PAGE

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OMB Number: 3235-0006
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Report for the Calendar Year or Quarter Ended: 06-30-2024
Check here if Amendment    Amendment Number:
This Amendment (Check only one.):    is a restatement.
   adds new holdings entries.
Institutional Investment Manager Filing this Report:
Name: Bain Capital Life Sciences Investors, LLC
Address: 200 Clarendon Street
Boston, MA  02116
Form 13F File Number: 028-18477
CRD Number (if applicable):
SEC File Number (if applicable):

The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:
Name: Adam Koppel
Title: Partner of Bain Capital Life Sciences Investors, LLC
Phone: 617-516-2000
Signature, Place, and Date of Signing:
/s/ Adam Koppel Boston MA 08-12-2024
[Signature] [City, State] [Date]
Bain Capital Life Sciences Investors, LLC ("BCLSI") is (i) the general partner of Bain Capital Life Sciences Partners, LP, which is the general partner of Bain Capital Life Sciences Fund, L.P., (ii) the general partner of BC SW, LP, (iii) the manager of Bain Capital Life Sciences Investors II, LLC, which is the general partner of Bain Capital Life Sciences Fund II, L.P., which is the manager of BCLS II Investco (GP), LLC, which is the general partner of BCLS II Investco, LP, and (iv) the manager of Bain Capital Life Sciences III General Partner, LLC, which is the general partner of Bain Capital Life Sciences Fund III, L.P., which is the sole member of Bain Capital Life Sciences Opportunities III GP, LLC, which is the general partner of Bain Capital Life Sciences Opportunities III, LP. The shares of Annexon Inc. ("ANNX") include an aggregate of 3,514,418 shares of ANNX common stock issuable upon conversion of warrants and pre-funded warrants. As of 6/30/24, affiliates of BCLSI held 4,935,330 shares of ANNX common stock. The shares of Savara Inc. ("SVRA") are as reported on Amendment No. 3 to the Schedule 13D filed by affiliates of BCLSI on 4/12/24 and reflect the exercise of securities held by such persons for SVRA common stock, after giving effect to provisions that prevent exercise if such persons would beneficially own more than 9.99% of the SVRA common stock. As of 6/30/24, such persons held 6,913,208 shares of SVRA common stock. The shares of Syros Pharmaceuticals, Inc. ("SYRS") are as reported on Amendment No. 3 to the Schedule 13G filed by affiliates of BCLSI on 2/13/24 and reflect the exercise of securities held by such persons for SYRS common stock, after giving effect to provisions that prevent exercise if such persons would beneficially own more than 9.99% of the SYRS common stock. As of 6/30/24, such persons held 1,687,547 shares of SYRS common stock. The shares of X4 Pharmaceuticals, Inc. ("XFOR") reflect the exercise of securities held by affiliates of BCLSI for XFOR common stock, after giving effect to provisions the prevent exercise if such persons would beneficially own more than 9.99% of the XFOR common stock. As of 6/30/24, such persons held 14,879,809 shares of XFOR common stock. The shares of Dianthus Therapeutics, Inc. ("DNTH") reflect the exercise of securities held by affiliates of BCLSI for DNTH common stock, after giving effect to provisions that prevent exercise if such person would beneficially own more than 9.99% of the DNTH common stock. As of 6/30/24, such person held 2,197,638 shares of DNTH Common Stock. The shares of Xilio Therapeutics, Inc. ("XLO") reflect the exercise of securities held by affiliates of BCLSI for XLO common stock, after giving effect to provisions that prevent exercise if such persons would beneficially own more than 9.99% of the XLO common stock. As of 6/30/24, such persons held 2,805,413 shares of XLO common stock.
Report Type (Check only one.):
X 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.)
   13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).)
   13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).)
Form 13F Summary Page
Report Summary:
Number of Other Included Managers: 11
Form 13F Information Table Entry Total: 25
Form 13F Information Table Value Total: 910,841,673
(round to nearest dollar)
List of Other Included Managers:
Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report.
[If there are no entries in this list, state “NONE” and omit the column headings and list entries.]
No. Name Form 13F File No. CRD No. (if applicable) SEC File No. (if applicable) CIK
1 Bain Capital Life Sciences Partners, LP 28-18476      
2 Bain Capital Life Sciences Fund, L.P. 28-18478      
3 BC SW, LP 28-20270      
4 Bain Capital Life Sciences Investors II, LLC 28-20816      
5 Bain Capital Life Sciences Fund II, L.P. 28-20814      
6 BCLS II Investco (GP), LLC 28-22976      
7 BCLS II Investco, LP 28-22978      
8 Bain Capital Life Sciences III General Partner, LLC 28-22975      
9 Bain Capital Life Sciences Fund III, L.P. 28-22979      
10 Bain Capital Life Sciences Opportunities III GP, LLC 28-22968      
11 Bain Capital Life Sciences Opportunities III, LP 28-22966