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CORRESP
 1
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 CORRESP

 Boundless Bio, Inc.
 10955 Alexandria Way, Suite 100
 San Diego, California 92121 April 8,
2025 VIA EDGAR Doris Stacey Gama
 Office of Life Sciences Division of Corporation Finance
 U.S. Securities and Exchange Commission 100 F Street, N.E.
 Washington, D.C. 20549

 Re:
 Boundless Bio, Inc.
 Registration Statement on Form S-3
 File No. 333-286302
 To the addressee set forth above: Pursuant to
Rule 461 of Regulation C of the General Rules and Regulations under the Securities Act of 1933, as amended, the undersigned, on behalf of Boundless Bio, Inc., respectfully requests that the effective date of the Registration Statement on Form S-3 referred to above be accelerated so that it will become effective at 4:00 P.M. Eastern Time on April 10, 2025, or as soon as practicable thereafter.
 If you have any questions or require additional information, please contact Cheston J. Larson of Latham & Watkins LLP at (858) 523-5435. Thank you for your assistance and cooperation in this matter.

 Sincerely,

 BOUNDLESS BIO, INC.

 By:

 /s/ Jessica Oien

 Jessica Oien

 Chief Legal Officer

 cc:
 Zachary D. Hornby, Boundless Bio, Inc.
 Matthew T. Bush, Latham & Watkins LLP
 Cheston J. Larson, Latham & Watkins LLP

<DOCUMENT>
<TYPE>TEXT-EXTRACT
<SEQUENCE>2
<FILENAME>filename2.txt
<TEXT>
 April 8, 2025

Zachary Hornby
Chief Executive Officer
Boundless Bio, Inc.
10955 Alexandria Way, Suite 100
San Diego, CA 92121

 Re: Boundless Bio, Inc.
 Registration Statement on Form S-3
 Filed April 1, 2025
 File No. 333-286302
Dear Zachary Hornby:

 This is to advise you that we have not reviewed and will not review your
registration
statement.

 Please refer to Rules 460 and 461 regarding requests for acceleration.
We remind you
that the company and its management are responsible for the accuracy and
adequacy of their
disclosures, notwithstanding any review, comments, action or absence of action
by the staff.

 Please contact Doris Stacey Gama at 202-551-3188 with any questions.

 Sincerely,

 Division of
Corporation Finance
 Office of Life
Sciences
cc: Cheston Larson
</TEXT>
</DOCUMENT>

January 23, 2025
Mark McDonnell
Managing Director
ARCH Venture Management, LLC
8755 W. Higgins Road Suite 1025
Chicago, IL 60631
Re:ARCH Venture Management, LLC
Boundless Bio, Inc.
Schedule 13D Filed by ARCH Venture Fund IX, L.P. et al.
Filed October 29, 2024
File No. 005-94492
Dear Mark McDonnell:
            We have conducted a limited review of the above-captioned filing and have the
following comment.
            Please respond to this letter by amending the filing or by providing the requested
information. If you do not believe our comment applies to your facts and circumstances or
that an amendment is appropriate, please advise us why in a response letter.
            After reviewing any amendment to the filing and any information provided in
response to this comment, we may have additional comments.
Schedule 13D Filed October 29, 2024
General
1.We note that the event reported as requiring the filing of the Schedule 13D was April
2, 2024. Rule 13d-1(a) of Regulation 13D-G requires the filing of a Schedule 13D
within five business days after the date beneficial ownership of more than five percent
of a class of equity securities specified in Rule 13d-1(i)(1) was acquired. Based on the
April 2, 2024 event date, the Schedule 13D submitted on October 29, 2024 was not
timely filed. Please advise us why the Schedule 13D was not filed within the required
five business days after the date of the acquisition.
            We remind you that the filing persons are responsible for the accuracy and adequacy
of their disclosures, notwithstanding any review, comments, action or absence of action by
the staff.

January 23, 2025
Page 2
            Please direct any questions to Brian Soares at 202-551-3690 or Nicholas Panos at
202-551-3266.
Sincerely,
Division of Corporation Finance
Office of Mergers & Acquisitions

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 Boundless Bio, Inc.

9880 Campus Point Drive, Suite 120

San Diego, CA 92121

 March 25, 2024

 VIA EDGAR

 Office of Life Sciences

Division of Corporation Finance

 U.S. Securities and Exchange
Commission

 100 F Street N.E.

 Washington, D.C. 20549

Re:
 Boundless Bio, Inc.

Registration Statement on Form S-1, as amended

File No. 333-277696

Ladies and Gentlemen:

 Pursuant to Rule 461 of
Regulation C of the General Rules and Regulations under the Securities Act of 1933, as amended, the undersigned, on behalf of Boundless Bio, Inc. (the “Company”), respectfully requests that the effective date of the
Registration Statement on Form S-1 referred to above be accelerated so that it will become effective at 4:00 P.M. Eastern Time on March 27, 2024, or as soon as practicable thereafter.

Please contact Matthew T. Bush of Latham & Watkins LLP, counsel to the Company, at (858)
523-3962, to provide notice of effectiveness, or if you have any questions or require additional information regarding this matter. Thank you for your assistance and cooperation in this matter.

Very truly yours,

BOUNDLESS BIO, INC.

By:

 /s/ Zachary D. Hornby

Zachary D. Hornby

President and Chief Executive Officer

cc:
 Zachary D. Hornby, Boundless Bio, Inc.

Jami Rubin, Boundless Bio, Inc.

Jessica Oien, Boundless Bio, Inc.

Cheston J. Larson, Latham & Watkins LLP

Charles S. Kim, Cooley LLP

Denny Won, Cooley LLP

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 March 25, 2024

United States Securities and Exchange Commission

 Division of
Corporation Finance

 100 F Street, N.E.

 Washington, DC 20549

 Attention:    Daniel Crawford

 Alan Campbell

 Ibolya Ignat

 Vanessa Robertson

Re:
 Boundless Bio, Inc.

Registration Statement on Form S-1, as amended (File
No. 333-277696)

 Ladies and Gentlemen:

Pursuant to Rule 460 of the General Rules and Regulations under the Securities Act of 1933, as amended, we wish to advise that on the date hereof,
approximately 2,100 copies of the Preliminary Prospectus, dated March 21, 2024, were distributed to prospective underwriters, institutional investors and prospective dealers in connection with the above-captioned Registration Statement.

We wish to advise you that the participating underwriters have informed us that they have complied and will continue to comply with the requirements of Rule 15c2-8 under the Securities Exchange Act of 1934, as amended.

 We hereby join in the request of the registrant that the
effectiveness of the above-captioned Registration Statement, as amended, be accelerated to 4:00 p.m. Eastern Time, on Wednesday, March 27, 2024 or as soon thereafter as practicable.

[signature page follows]

Very truly yours,

GOLDMAN SACHS & CO. LLC

LEERINK PARTNERS LLC

PIPER SANDLER & CO.

GUGGENHEIM SECURITIES, LLC

As representatives of the Underwriters

GOLDMAN SACHS & CO. LLC

By:

 /s/ Lyla Bibi Maduri

Name:

Lyla Bibi Maduri

Title:

Managing Director

LEERINK PARTNERS LLC

By:

 /s/ Murphy Gallagher

Name:

Murphy Gallagher

Title:

Senior Managing Director

PIPER SANDLER & CO.

By:

 /s/ Chad Huber

Name:

Chad Huber

Title:

Managing Director

GUGGENHEIM SECURITIES, LLC

By:

 /s/ Jordan Bliss

Name:

Jordan Bliss

Title:

Senior Managing Director

 [Signature Page to Acceleration Request Letter]

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 March 15, 2024

VIA EDGAR

 Daniel Crawford

Office of Life Sciences

 Division of Corporation Finance

U.S. Securities and Exchange Commission

 100 F Street N.E.

Washington, D.C. 20549

12670 High Bluff Drive

San Diego, California 92130

Tel: +1.858.523.5400 Fax: +1.858.523.5450

www.lw.com

FIRM / AFFILIATE OFFICES

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Madrid

Re:
 Boundless Bio, Inc.

 
 Registration Statement on Form S-1

 
 Filed March 6, 2024

 
 File No. 333-277696

Dear Mr. Crawford:

 We are in receipt of
the Staff’s letter dated March 13, 2024 with respect to the above-referenced Registration Statement on Form S-1 (the “Registration Statement”). We are responding to the
Staff’s comments on behalf of Boundless Bio, Inc. (“Boundless” or the “Company”) as set forth below.

The Company’s response set forth in this letter is numbered to correspond to the numbered comment in the Staff’s letter. All terms
used but not defined herein have the meanings assigned to such terms in the Registration Statement. For ease of reference, we have set forth the Staff’s comment and the Company’s response below.

Registration Statement on Form S-1

Management’s Discussion and Analysis of Financial Condition and Results of Operations Critical Accounting Policies and Significant Estimates and
Judgments

 Stock-Based Compensation Expense, page 96

1.
 Please refer to your letter submitted on March 8, 2024. Please explain why the preliminary fair values
for the February 2024 grants were based upon a straight-line interpolation from the September 15, 2023 Valuation and not the more recent January 19, 2024 Valuation.

 March 15, 2024

Page 2

 Boundless’ Response: The Company respectfully advises the Staff that the Company elected
to use the September 15, 2023 valuation in reassessing the February 2024 grants as that was the first point in time the Company’s development progress gave it better visibility into the potential for an IPO (coupled with the initial filing
of a draft Registration Statement), and since that time the continued progress on the Company’s research and development programs and an increased likelihood of an IPO resulted in a ratable increase in value throughout the applicable
quarters. In response to the Staff’s comment, the Company has updated the disclosure in “Management’s Discussion and Analysis of Financial Condition and Results of Operations” that it plans to file in the next pre-effective amendment to the Registration Statement, as follows:

 “In February 2024, we granted
stock options to purchase approximately 16.4 million shares of our common stock at an exercise price of $0.42 per share, which generally vest over a requisite service period of four years. The exercise prices for the stock options we granted in
February 2024 were equal to the fair value of a share of our common stock on the grant date as determined by our board of directors on the date of grant. In light of progress made towards completion of an IPO and information received in estimation
of our initial public offering price range, we preliminarily established the fair value of the February 2024 grants for financial reporting purposes based on a straight-line interpolation from a third-party valuation of our common stock on
September 15, 2023 to the midpoint of the initial price range for this offering in order to determine the appropriate stock-based compensation expense. The Company elected to use the September 15, 2023 third-party valuation as that was the
first point in time the Company’s development progress gave it better visibility into the potential for an IPO (coupled with the initial filing of a draft Registration Statement), and since that time the continued progress on the Company’s
research and development programs and an increased likelihood of an IPO resulted in a ratable increase in value throughout the applicable quarter. Therefore, while we have not yet prepared financial statements for the first quarter of 2024, we
expect, solely for financial reporting purposes, to recognize stock-based compensation expense for the February 2024 grants of approximately $9.5 million, to be amortized over a weighted average term of 3.9 years. The amount of stock-based
compensation expense related to these options is based upon our estimates, and could change as events and circumstances change. Upon completion of this offering, our common stock will be publicly traded and we will rely on the closing price of our
common stock as reported on the date of grant to determine the fair value of our common stock.”

 *********

 March 15, 2024

Page 3

 Any comments or questions regarding the foregoing should be directed to the undersigned at
(858) 523-3962. Thank you in advance for your cooperation in connection with this matter.

Very truly yours,

/s/ Matthew T. Bush

 Matthew T. Bush

 of LATHAM & WATKINS
LLP

cc:
 Zachary Hornby, Boundless Bio, Inc.

Jami Rubin, Boundless Bio, Inc.

Jessica Oien, Boundless Bio, Inc.  

Cheston J. Larson, Latham & Watkins LLP

Charles S. Kim, Cooley LLP

Denny Won, Cooley LLP

United States securities and exchange commission logo
March 13, 2024
Zachary Hornby
President and Chief Executive Officer
Boundless Bio, Inc.
9880 Campus Point Drive, Suite 120
San Diego, CA 92121
Re:Boundless Bio, Inc.
Registration Statement on Form S-1
Filed March 6, 2024
File No. 333-277696
Dear Zachary Hornby:
            We have reviewed your registration statement and have the following comment.
            Please respond to this letter by amending your registration statement and providing the
requested information. If you do not believe the comment applies to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
            After reviewing any amendment to your registration statement and the information you
provide in response to this letter, we may have additional comments.
Registration Statement on Form S-1
Management's Discussion and Analysis of Financial Condition and Results of Operations
Critical Accounting Policies and Significant Estimates and Judgments
Stock-Based Compensation Expense, page 96
1.Please refer to your letter submitted on March 8, 2024. Please explain why the preliminary
fair values for the February 2024 grants were based upon a straight-line interpolation from
the September 15, 2023 Valuation and not the more recent January 19, 2024 Valuation.

 FirstName LastNameZachary Hornby
 Comapany NameBoundless Bio, Inc.
 March 13, 2024 Page 2
 FirstName LastName
Zachary Hornby
Boundless Bio, Inc.
March 13, 2024
Page 2
            We remind you that the company and its management are responsible for the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action or absence of
action by the staff.
            Refer to Rules 460 and 461 regarding requests for acceleration. Please allow adequate
time for us to review any amendment prior to the requested effective date of the registration
statement.
            Please contact Ibolya Ignat at 202-551-3636 or Vanessa Robertson at 202-551-3649 if
you have questions regarding comments on the financial statements and related matters. Please
contact Daniel Crawford at 202-551-7767 or Alan Campbell at 202-551-4224 with any other
questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Matthew Bush, Esq.

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CORRESP

 12670 High Bluff Drive

San Diego, California 92130

Tel: +1.858.523.5400 Fax: +1.858.523.5450

www.lw.com

FIRM / AFFILIATE OFFICES

Austin

Milan

Beijing

Munich

Boston

New York

Brussels

Orange County

Century City

Paris

Chicago

Riyadh

 FOIA CONFIDENTIAL TREATMENT REQUEST

The entity requesting confidential treatment is:

Boundless Bio, Inc.

Dubai

San Diego

Düsseldorf

San Francisco

Frankfurt

Seoul

Hamburg

Silicon Valley

Hong Kong

Singapore

Houston

Tel Aviv

London

Tokyo

Los Angeles

Washington, D.C.

[***] Certain information in this document has been omitted and filed separately with the Securities and Exchange Commission. Confidential treatment has been requested by Boundless Bio, Inc. with respect to this
letter.

Madrid

 March 8, 2024

 VIA
EDGAR

 Daniel Crawford

 Office of Life Sciences

Division of Corporation Finance

 U.S. Securities and Exchange
Commission

 100 F Street N.E.

 Washington, D.C. 20549

Re:
 Boundless Bio, Inc. | Anticipated Price Range

Registration Statement on Form S-1 (File
No. 333-277696)

 Dear Mr. Crawford:

Rule 83 Confidential Treatment Requested by Boundless Bio, Inc.

This letter is furnished supplementally on behalf of Boundless Bio, Inc. (the “Company”) in response to comments from
the staff (the “Staff”) of the U.S. Securities and Exchange Commission (the “Commission”) received by letter dated September 29, 2023, and in connection with the review by the Commission of the
above-mentioned Registration Statement on Form S-1 (the “Registration Statement”). To assist the Staff in its review, the Company advises the Staff that it presently estimates,
considering information currently available and current market conditions and based in part on information received by the lead underwriters, that the initial public offering price per share for the initial public offering
(“IPO”) pursuant to the Registration Statement will be between $[***] and $[***] (without giving effect to any reverse stock split that the Company will effect prior to the offering, the “Preliminary Price
Range”). For clarity, the Company advises the Staff that, given the volatility of the public trading markets and the uncertainty of the timing of the IPO, the Company and the lead underwriters have not yet finally agreed to a price
range for the IPO. The Company advises the Staff that the final range to be included in a pre-effective amendment to the Registration Statement, after giving effect to an appropriate stock split, will include
a price range of no more than $2.00 or 20% of the high end of the range, unless otherwise approved by the Staff.

 U.S. Securities and Exchange Commission

FOIA CONFIDENTIAL TREATMENT REQUEST

  Page
 2

 Recent Stock Option Grants

The Company’s grants of stock options during the 12 months preceding the latest balance sheet date presented in the Registration
Statement, as well as those made since the latest balance sheet, are set forth below.

 Grant Date

Number of Shares
Underlying
Options Granted

Per Share
Exercise Price
of Options

Per Share Fair
Value of Shares
on Grant Date

 January 16, 2023

433,716

$
0.51
*

$
0.51
*

 February 15, 2023

26,300

$
0.51
*

$
0.51
*

 May 17, 2023

290,900

$
0.21

$
0.21

 June 13, 2023

19,606,000

$
0.21

$
0.21

 June 21, 2023

2,120,642

$
0.21

$
0.21

 July 15, 2023

839,536

$
0.21

$
0.21

 July 26, 2023

3,835,000

$
0.21

$
0.21

 October 2, 2023

1,080,000

$
0.23

$
0.23

 October 16, 2023

515,000

$
0.23

$
0.23

 November 15, 2023

190,000

$
0.23

$
0.23

 December 13, 2023

1,050,000

$
0.23

$
0.23

 February 5, 2024

2,715,790

$
0.42

$
0.42

 February 15, 2024

13,670,050

$
0.42

$
0.42

*
 Represents original exercise prices and per share values. These options were repriced on June 13, 2023
to modify the exercise prices to $0.21 per share.

 Common Stock Valuation Methodologies

The Company has historically determined the fair value of its common stock using methodologies, approaches and assumptions consistent with the
American Institute of Certified Public Accountants Accounting and Valuation Guide, Valuation of Privately Held Company Equity Securities Issued as Compensation (the “AICPA Practice Guide”). In addition, the
Company’s Board of Directors (the “Board”) considered numerous objective and subjective factors, along with input from management and third-party valuations, to determine the fair value of the Company’s common stock
as further disclosed on pages 97 and 98 of the Registration Statement.

 Based on the Company’s early stage of development, the
difficulty in predicting the range of specific outcomes (and their likelihood) and other relevant factors, a hybrid method computing the probability-weighted value across two scenarios (the Current Value Method (“CVM”)
scenario and the Option Pricing Method (“OPM”) scenario or, as described below, a market-adjusted OPM scenario) was considered most appropriate for valuations through April 2023. In addition, as a result of the closings of
the Company’s Series C convertible preferred stock financing in April and May 2023 (“Series C Financing”) at a per share purchase price of $0.70, in the valuation completed in April 2023, the Company used the backsolve
method to determine equity value in the OPM scenario. The backsolve method is a market approach that derives an implied total equity value from the sale price of the Company’s equity

 U.S. Securities and Exchange Commission

FOIA CONFIDENTIAL TREATMENT REQUEST

  Page
 3

securities in a recent arm’s length transaction. For valuations performed beginning in September 2023, the Company used a hybrid method of the OPM scenario and an IPO scenario given the
development progress of the Company and better visibility into the potential for an IPO. For each IPO scenario used in the valuations, the Company estimated its equity value based on, among other things, the value of public companies deemed similar
to the Company at the time of their IPOs.

 In order for the Board to determine the estimated fair value of the Company’s common
stock, the Company obtained independent third-party valuations of its common stock as of March 31, 2022 (the “March 31, 2022 Valuation”), April 5, 2023 (the
“April 5, 2023 Valuation”), September 15, 2023 (the “September 15, 2023 Valuation”), December 1, 2023 (the
“December 1, 2023 Valuation”), and January 19, 2024 (the “January 19, 2024 Valuation”).

At each option grant date, the Board considered whether any events occurred that would trigger any material changes to the business or would
require adjustment to the estimated fair value of the Company’s common stock from the previous valuation date. The Company does not expect to make any additional grants prior to the completion of its IPO other than grants made concurrent with
the IPO at an exercise price equal to the final IPO price.

 Grant Date Fair Value Determinations

January and February 2023 Option Grants

The Board, with input from management, determined the fair value of the Company’s common stock to be $0.51 per share for options granted
on January 16, 2023 and February 15, 2023, after considering the March 31, 2022 Valuation. In reaching this determination, the Board determined that no material changes had occurred in the business since the report date of the
March 31, 2022 Valuation and that the March 31, 2022 Valuation was still appropriate.

 For the March 31, 2022 Valuation,
the Company utilized an OPM method to derive the implied equity value for the Company, whereby it applied a market adjustment to the prior April 30, 2021 valuation given the Company had not completed a recent equity financing. The Company
applied a 10% downward adjustment to the OPM allocable value from the prior valuation given declines in selected guideline public companies market capitalizations and biotechnology index during the period, which resulted in an allocable equity value
of approximately $[***] million. In addition, an option-based approach based on an average of the Finnerty and Asian put models was performed to estimate a 35% discount for lack of marketability (“DLOM”) for the common stock.
The Company estimated the expected timing of a potential liquidity event was 1.5 years, based on management’s best estimates and an analysis of market conditions. The concluded fair value was $0.51 per share.

Repricing

 On
June 13, 2023, in order to retain and properly incentivize the Company’s employees, the Board approved a repricing of stock options held by current employees with exercise prices in excess of $0.21 per share, whereby the exercise price per
share of each outstanding stock option with an exercise price higher than $0.21 per share was lowered to $0.21 per share (the fair market value per share on the date of the repricing as determined by the Board based on the April 5, 2023
Valuation discussed below). As disclosed in the Registration Statement, the repricing resulted in one-time stock-based compensation expense of approximately $263,000 related to vested options and incremental
stock option expense of approximately $377,000 related to unvested options, which will be amortized on a straight-line basis over the remaining vesting period of those options.

 U.S. Securities and Exchange Commission

FOIA CONFIDENTIAL TREATMENT REQUEST

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 May, June and July 2023 Option Grants

The Board, with input from management, determined the fair value of the Company’s common stock to be $0.21 per share as of May 17,
2023, June 13, 2023, June 21, 2023, July 15, 2023 and July 26, 2023, after considering the April 5, 2023 Valuation. In reaching this determination, the Board determined that no material changes had occurred in the business
since the report date of the April 5, 2023 Valuation and that the April 5, 2023 Valuation was still appropriate. Among the qualitative factors considered by the Board in determining the fair value of the Company’s common stock as part
of the April 5, 2023 Valuation was the closing of the Series C Financing in April 2023.

 The Company utilized a $[***] million and
$[***] million equity value and assigned a [***]% and [***]% probability weighting to the OPM and CVM scenarios, respectively, and used a DLOM of 45% in each scenario (based on the application of the Finnerty and Asian put option analyses). This
resulted in a present value per share of $[***] and $[***] and weighted adjusted present value per share of $[***] and $[***] in the OPM and CVM scenarios, respectively. The Company estimated the expected timing of a potential liquidity event was
1.8 years in the OPM scenario, based on management’s best estimates and an analysis of market conditions.

 October and November
2023 Option Grants

 The Board, with input from management, determined the fair value of the Company’s common stock to
be $0.23 per share as of October 2, 2023, October 16, 2023 and November 15, 2023, after considering the September 15, 2023 Valuation. In reaching this determination, the Board determined that no material changes had occurred in
the business since the report date of the September 15, 2023 Valuation and that the September 15, 2023 was still appropriate.

As discussed above, the Company included an IPO scenario beginning with the September 15, 2023 Valuation. Although management believed an
eventual IPO was possible, there remained significant uncertainty as of the valuation date based on the early stage of the Company’s POTENTIATE clinical trial and uncertain market conditions with respect to whether the IPO window would be open
in 2024 for companies without later-stage clinical data. Importantly, while the Company had filed an initial draft Registration Statement on September 1, 2023 and an amendment to the draft Registration Statement on October 11, 2023, by the
time the final report for the September 15, 2023 Valuation was issued on November 15, 2023, based on the status of the POTENTIATE clinical trial and other development programs, the Company had decided not to proceed with the filing of
another amendment to the draft Registration Statement as it believed the likelihood of a near-term IPO was very unlikely. In addition, unlike other companies at this stage of the IPO process, the Company elected not to conduct any testing-the-waters (“TTW”) meetings with investors and ended up not refiling another amendment to the draft Registration Statement until
January 22, 2024. Thus, the Company assigned a [***]% probability weighting to the IPO scenario, with the remaining [***]% to the OPM scenario. The Company utilized a $[***] million and $[***] million equity value and DLOM of 45% and 15% for
the OPM and IPO scenarios, respectively (based on the application of the Finnerty and Protective and Asian put option analyses for the OPM scenario and published comment letters of the Commission for the IPO scenario due to the term to liquidity of
less than 12 months). This resulted in a present value per share of $[***] and $[***] and weighted adjusted present value per share of $[***] and $[***] in the IPO and OPM scenarios, respectively. The Company estimated the expected timing of a
potential liquidity event was 0.62 years in the IPO scenario (April 30, 2024) and 1.3 years in the OPM scenario, based on management’s best estimates and an analysis of market conditions.

 U.S. Securities and Exchange Commission

FOIA CONFIDENTIAL TREATMENT REQUEST

  Page
 5

 December 2023 Option Grants

The Board, with input from management, determined the fair value of the Company’s common stock to be $0.23 per share as of
December 13, 2023, after considering the December 1, 2023 Valuation. In reaching this determination, the Board determined that no material changes had occurred in the business since the report date of the December 1, 2023 Valuation
and that the December 1, 2023 Valuation was still appropriate.

 For the reasons discussed above, the Company left the probabilities
of the IPO and OPM scenarios unchanged as no events had occurred since the prior valuation to alter the likelihood of those scenarios. The Company utilized a $[***] million and $[***] million equity value and DLOM of 40% and 15% for the OPM and IPO
scenarios, respectively (based on the application of the Finnerty and Protective and Asian put option analyses for the OPM scenario and published comment letters of the Commission for the IPO scenario due to the term to liquidity of less than 12
months). This resulted in a present value per share of $[***] and $[***] and weighted adjusted present value per share of $[***] and $[***] in the IPO and OPM scenarios, respectively. The Company estimated the expected timing of a potential
liquidity event was 0.41 years in the IPO scenario (April 30, 2024) and 1.0 year in the OPM scenario, based on management’s best estimates and an analysis of market conditions.

February 2024 Option Grants

The Board, with input from management, determined the fair value of the Company’s common stock to be $0.42 per share as of
February 5, 2024 and February 15, 2024, after considering the January 19, 2024 Valuation. In reaching this determination, the Board determined that no material changes had occurred in the business since the report date of the
January 19, 2024 Valuation and that the January 19, 2024 Valuation was still appropriate.

 Among the qualitative factors
considered by the Board in determining the fair value of the Company’s common stock for the February 2024 grants were the following developments in the Company’s business subsequent to December 13, 2023: 

•

 the Company determined to re-submit an amended draft Registration
Statement, which it did on January 22, 2024, and started to prepare for TTW meetings with investors;

•

 the continued progress in the POTENTIATE clinical trial; and

•

 the Company received IND clearance from the FDA for BBI-825.

 Given the above developments, the Company assigned a [***]% probability weighting to the IPO scenario,

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12670 High Bluff Drive

San Diego, California 92130

Tel: +1.858.523.5400 Fax: +1.858.523.5450

www.lw.com

FIRM / AFFILIATE OFFICES

Austin

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March 6, 2024

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Daniel Crawford

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Office of Life Sciences

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 Division of Corporation Finance

U.S. Securities and Exchange Commission

 100 F Street N.E.

Washington, D.C. 20549

Re:
 Boundless Bio, Inc.

Amendment No. 2 to Draft Registration Statement on Form S-1

Submitted January 23, 2024

CIK No. 0001782303

 Dear
Mr. Crawford:

 We are in receipt of the Staff’s letter dated January 29, 2024 with respect to the above-referenced
confidential draft Amendment No. 2 to Draft Registration Statement on Form S-1. We are responding to the Staff’s comments on behalf of Boundless Bio, Inc. (“Boundless” or the
“Company”) as set forth below. Simultaneously with the submission of this letter, the Company is publicly filing via EDGAR a Registration Statement on Form S-1 (the
“Registration Statement”) responding to the Staff’s comments and updating the Company’s disclosures in the Registration Statement.

The Company’s responses set forth in this letter are numbered to correspond to the numbered comments in the Staff’s letter. All
terms used but not defined herein have the meanings assigned to such terms in the Registration Statement. For ease of reference, we have set forth the Staff’s comments and the Company’s response for each item below.

Amendment No. 2 to Draft Registration Statement on Form S-1

Prospectus Summary

 Our Pipeline and
Platform, page 3

1.
 Please revise your pipeline table here and elsewhere in the registration statement so that it contains no
more than two preclinical columns that show a progress bar.

 Boundless’ Response: The Company has revised the
pipeline table on pages 3, 102 and 121 of the Registration Statement in response to the Staff’s comment.

 March 6, 2024

Page 2

 *********

Any comments or questions regarding the foregoing should be directed to the undersigned at (858)
523-3962. Thank you in advance for your cooperation in connection with this matter.

Very truly yours,

/s/ Matthew T. Bush

 Matthew T. Bush

 of LATHAM & WATKINS
LLP

cc:
 Zachary Hornby, Boundless Bio, Inc.

Jami Rubin, Boundless Bio, Inc.

Jessica Oien, Boundless Bio, Inc.

Cheston J. Larson, Latham & Watkins LLP

Charles S. Kim, Cooley LLP

Denny Won, Cooley LLP

United States securities and exchange commission logo
January 29, 2024
Zachary Hornby
President and Chief Executive Officer
Boundless Bio, Inc.
9880 Campus Point Drive, Suite 120
San Diego, CA 92121
Re:Boundless Bio, Inc.
Amendment No. 2 to Draft Registration Statement on Form S-1
Submitted January 23, 2024
CIK No. 0001782303
Dear Zachary Hornby:
            We have reviewed your amended draft registration statement and have the following
comment.
            Please respond to this letter by providing the requested information and either submitting
an amended draft registration statement or publicly filing your registration statement on
EDGAR. If you do not believe our comment applies to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.
            After reviewing the information you provide in response to this letter and your amended
draft registration statement or filed registration statement, we may have additional comments.
Amendment No. 2 to Draft Registration Statement on Form S-1
Prospectus Summary
Our Pipeline and Platform, page 3
1.Please revise your pipeline table here and elsewhere in the registration statement so that it
contains no more than two preclinical columns that show a progress bar.
            Please contact Ibolya Ignat at 202-551-3636 or Vanessa Robertson at 202-551-3649 if
you have questions regarding comments on the financial statements and related matters. Please
contact Daniel Crawford at 202-551-7767 or Alan Campbell at 202-551-4224 with any other
questions.

 FirstName LastNameZachary Hornby
 Comapany NameBoundless Bio, Inc.
 January 29, 2024 Page 2
 FirstName LastName
Zachary Hornby
Boundless Bio, Inc.
January 29, 2024
Page 2
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Matthew Bush, Esq.

United States securities and exchange commission logo
September 29, 2023
Zachary Hornby
President and Chief Executive Officer
Boundless Bio, Inc.
9880 Campus Point Drive, Suite 120
San Diego, CA 92121
Re:Boundless Bio, Inc.
Draft Registration Statement on Form S-1
Submitted September 1, 2023
CIK No. 0001782303
Dear Zachary Hornby:
            We have reviewed your draft registration statement and have the following comments.  In
some of our comments, we may ask you to provide us with information so we may better
understand your disclosure.
            Please respond to this letter by providing the requested information and either submitting
an amended draft registration statement or publicly filing your registration statement on
EDGAR.  If you do not believe our comments apply to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.
            After reviewing the information you provide in response to these comments and your
amended draft registration statement or filed registration statement, we may have additional
comments.
Draft Registration Statement on Form S-1 submitted September 1, 2023
Prospectus Summary
Overview, page 1
1.We note your disclosure here and throughout your Prospectus stating, among other things,
that your product candidates demonstrated “potent” inhibition and showed "substantial . . .
anti-tumor activity[.]"  Please revise these and similar statements throughout your
prospectus to eliminate conclusions or predictions that your product candidates are
effective, as determinations of efficacy are solely within the authority of the FDA.  You
may provide an objective summary of the data that you used to draw such conclusions.
2.Please revise pages 2 and 103 to provide the basis for your belief that you “are the world’s

 FirstName LastNameZachary Hornby
 Comapany NameBoundless Bio, Inc.
 September 29, 2023 Page 2
 FirstName LastNameZachary Hornby
Boundless Bio, Inc.
September 29, 2023
Page 2
leading ecDNA experts” and that Dr. Paul Mischel is “the globally recognized leader in
the ecDNA field.”
3.Please revise to define “synthetic lethal” the first time it is used.
4.We note your disclosure that since your inception, you have raised "$252.1 million from
leading life science investors, including [y]our 5% or greater stockholders, ARCH
Venture Partners, Fidelity Management & Research Company LLC, RA Capital
Management, Leaps by Bayer, Nextech Invest, and Vertex Ventures HC, as well as other
investors."  Please relocate this disclosure from your prospectus summary to your
"Principal Stockholders" section.  We note in this regard that the identification of the pre-
IPO investors in your prospectus summary may appear to suggest that
potential investors in your public offering consider investments made by the pre-
IPO investors as a factor in making an investment decision without knowing, among other
things, the amount of each pre-IPO investor’s investment in total or on a per share basis,
their investment strategies or whether those investors will continue to hold their shares in
the future, as some of the pre-IPO investors may not be subject to the reporting
requirements of Section 16 of the Exchange Act, and investors in your public offering will
not necessarily know when some of the pre-IPO investors decide to sell any of their
shares.
Our Pipeline and Platform, page 2
5.Please revise your pipeline tables on pages 2, 103 and 121 to make the following changes:
•Remove your BBI-098 program as it appears your disclosure on page 135 indicates
you are not currently developing this product candidate or, alternatively, please
advise;
•revise the presentation of your ecDNA diagnostic row so it does not appear to
indicate the completion of phase 3 clinical trials; and
•clarify here, and elsewhere as appropriate, whether the ecDNA diagnostic is a
medical device that will need to be approved for use by the FDA.
Our Strategy, page 4
6.Please revise here to include an equally prominent discussion of the challenges and
uncertainties involved in executing your business strategy.
Management's Discussion and Analysis of Financial Condition and Results of Operations
Critical Accounting Policies and Significant Estimates and Judgments
Stock-Based Compensation Expense, page 98
7.Once you have an estimated offering price or range, please explain to us how you
determined the fair value of the common stock underlying your equity issuances and the
reasons for any differences between the recent valuations of your common stock leading
up to the initial public offering and the estimated offering price. This information will help
facilitate our review of your accounting for equity issuances including stock

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 September 29, 2023 Page 3
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Boundless Bio, Inc.
September 29, 2023
Page 3
compensation. Please discuss with the staff how to submit your response.
Business
Our Strategy, page 104
8.Please revise pages 105 and 144 to disclose the significance of the FDA’s determination
that your ecDNA diagnostic is a non-significant risk device.  Please clarify whether
your companion diagnostic will require FDA medical device approval as you appear to
suggest on page 27.
Our Lead ecDTx: BBI-355 CHK1 Inhibitor, page 122
9.We note your disclosure that your lead product, BBI-355, is being studied in the Phase 1/2
POTENTIATE clinical trial in patients with oncogene amplified cancers.  Please revise
your disclosure here and on page 132 to specify the cancer indications being evaluated in
this clinical trial.
BBI-355 Clinical Development Plan, page 132
10.Please revise to disclose how many patients are currently enrolled in the POTENTIATE
clinical trial.
11.We note your disclosure on page 133 stating that, depending on clinical trial results, you
“would seek to engage with the FDA and other global regulatory bodies to discuss
potential registrational paths."  Please revise your disclosure to note that even if "any
cohort of the trial demonstrate[s] compelling signs of clinical anti-tumor activity" and
"acceptable safety and tolerability" is demonstrated in this trial, the FDA and other similar
regulatory agencies may require further clinical trials to be completed prior to having
discussions with you about "potential registrational paths" regarding your product
candidate.
12.We note your disclosure on page 133 that you have entered into clinical trial collaboration
and supply agreements with each of Eli Lily and Taiho Oncology.  Please revise your
disclosure to describe the material terms of those agreements including, but not limited to,
the term and termination provisions as well as any milestone or royalty payment
provisions.
Addressable Patient Populations for BBI-355, page 134
13.Please revise the graphics on pages 135 and 142 to remove any indications that you are
not currently pursuing.
BBI-825 In Vitro Preclinical Data, page 137
14.Please revise your graphic on page 138 to provide the p-value or state whether the results
of the BBI-825 in vitro tests are statistically significant.  Likewise, revise your discussion
of your third ecDTx program to indicate whether the preclinical results disclosed in the

 FirstName LastNameZachary Hornby
 Comapany NameBoundless Bio, Inc.
 September 29, 2023 Page 4
 FirstName LastName
Zachary Hornby
Boundless Bio, Inc.
September 29, 2023
Page 4
graphic on page 143 are statistically significant.
Our Third ecDTx Program, page 142
15.We note your disclosure on page 143 that you "preclinically validated [a] target both in
vitro and in vivo across multiple ecDNA models[.]"  Please revise your disclosure to
clarify the meaning of the phrase "preclinically validated" in this instance.
Intellectual Property, page 145
16.Please revise your intellectual property disclosure starting on page 145 to disclose all
foreign jurisdictions where you have pending patents for each program and disclose when
you expect the patents associated with your Precision Medicine Program to expire.
Principal Stockholders, page 190
17.Please revise footnote 6 on page 192 to identify the natural persons comprising the
investment committee established by VVM.
Description of Capital Stock
Choice of Forum, page 197
18.We note that your forum selection provision identifies the Court of Chancery of the State
of Delaware as the exclusive forum for certain litigation, including any “derivative
action.” Please revise here and your risk factor on page 70 to disclose whether this
provision applies to actions arising under the Exchange Act.  In that regard, we note that
Section 27 of the Exchange Act creates exclusive federal jurisdiction over all suits brought
to enforce any duty or liability created by the Exchange Act or the rules and regulations
thereunder.
General
19.Please provide us with supplemental copies of all written communications, as defined in
Rule 405 under the Securities Act, that you, or anyone authorized to do so on your
behalf, have presented or expect to present to potential investors in reliance on Rule
163B of the Securities Act, whether or not you retained, or intend to retain, copies of those
communications.

 FirstName LastNameZachary Hornby
 Comapany NameBoundless Bio, Inc.
 September 29, 2023 Page 5
 FirstName LastName
Zachary Hornby
Boundless Bio, Inc.
September 29, 2023
Page 5
            You may contact Ibolya Ignat at 202-551-3636 or Vanessa Robertson at 202-551-3649 if
you have questions regarding comments on the financial statements and related matters.  Please
contact Daniel Crawford at 202-551-7767 or Joshua Gorsky at 202-551-7836 with any other
questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Matthew Bush, Esq.