CONFIDENTIAL — FOR PROSPECTIVE INVESTORS ONLY

ISSUER FREE WRITING PROSPECTUS

Filed Pursuant to Rule 433

Registration Statement No. 333-274851 (Form S-3)

Supplementing the Preliminary Prospectus Supplement dated October 2, 2023 and the accompanying Base Prospectus

October 12, 2023

Penterra Pharmaceuticals Corp.

Pricing Term Sheet

The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling Ridgeline Securities LLC toll-free at 1-800-555-0147 or Broadmark Capital Inc. toll-free at 1-800-555-0263.

Offering Overview

This pricing term sheet sets forth the final terms of the offering of shares of common stock of Penterra Pharmaceuticals Corp. ("Penterra" or the "Company") by the selling stockholders named in the prospectus supplement and should be read together with the preliminary prospectus supplement dated October 2, 2023 (the "Preliminary Prospectus Supplement") and the accompanying base prospectus (the "Base Prospectus") forming part of Registration Statement No. 333-274851. This term sheet supersedes and replaces in their entirety the estimated and indicative terms set forth in the Preliminary Prospectus Supplement to the extent inconsistent herewith.

Penterra Pharmaceuticals Corp. is not selling any shares in connection with this offering and will not receive any proceeds from the sale of shares of common stock by the selling stockholders. All shares of common stock being offered are being sold by the selling stockholders identified below.

The information in this pricing term sheet reflects the final pricing of the offering, which was determined after the close of trading on October 12, 2023 through a process of negotiations among the selling stockholders and the representatives of the underwriters.

Final Pricing Terms

Issuer Information.

Offering Terms.

Pricing.

The underwriting discount set forth above does not reflect any reimbursement of expenses of the underwriters by the selling stockholders. The selling stockholders have agreed to reimburse the underwriters for certain of their out-of-pocket expenses, including FINRA counsel fees, in an amount not to exceed $50,000 in the aggregate.

Key Dates.

Settlement of the shares of common stock is expected to occur on October 17, 2023, which will be the third business day following the date of pricing and the trade date. Under Rule 15c6-1 under the Securities Exchange Act of 1934, as amended, trades in the secondary market are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade shares of common stock prior to the delivery date may be required, by virtue of the fact that the shares initially will settle in T+3, to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement. Purchasers of shares of common stock who wish to make such trades should consult their own advisors.

Selling Stockholder Share Breakdown

The following table sets forth the number of shares of common stock to be sold by each selling stockholder in the base offering and the number of additional shares that each selling stockholder has granted the underwriters the option to purchase pursuant to the over-allotment option:

The over-allotment shares to be sold by each selling stockholder, if any, are proportionate to each selling stockholder's share of the base offering. The underwriters may exercise the over-allotment option in whole or in part, on one or more occasions, on or before November 11, 2023.

Underwriter Allocation. The following table sets forth the number of shares of common stock that each underwriter has severally agreed to purchase from the selling stockholders in the base offering:

Ridgeline Securities LLC and Broadmark Capital Inc. are acting as joint book-running managers for the offering. Linden Groves & Co. and Harborview Partners LLC are acting as co-managers for the offering. The underwriters are severally, and not jointly, obligated to purchase the number of shares set forth opposite their names above, subject to the conditions set forth in the underwriting agreement among the selling stockholders and the underwriters.

Each underwriter's proportionate share of the over-allotment option, if exercised, will be in the same proportion as the number of base shares set forth opposite such underwriter's name above bears to the total number of base shares.

Lock-Up Provisions

Each of the selling stockholders has agreed, subject to certain customary exceptions, that during the period beginning on the closing date of this offering (expected to be October 17, 2023) and ending 90 days thereafter (i.e., on January 15, 2024) (the "Lock-Up Period"), such selling stockholder will not, without the prior written consent of Ridgeline Securities LLC and Broadmark Capital Inc., as representatives of the underwriters:

(a) offer, pledge, announce the intention to sell, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, or otherwise transfer or dispose of, directly or indirectly, any shares of common stock of the Company or any securities convertible into or exercisable or exchangeable for shares of common stock of the Company that are owned or controlled by such selling stockholder following the closing of this offering;

(b) enter into any swap, hedge, or other arrangement that transfers, in whole or in part, any of the economic consequences of ownership of common stock of the Company, whether any such transaction described in clause (a) above or this clause (b) is to be settled by delivery of shares of common stock of the Company, in cash or otherwise; or

(c) make any demand for, or exercise any right with respect to, the registration of any shares of common stock of the Company or any security convertible into or exercisable or exchangeable for common stock of the Company.

The foregoing restrictions are subject to customary exceptions, including, without limitation, transfers of shares as bona fide gifts to immediate family members or to trusts for the benefit of immediate family members, transfers by will or intestacy, distributions by Castellano Family Holdings LLC to its members, and transfers to any affiliate of the selling stockholder, provided in each case that the transferee agrees in writing to be bound by the terms of the lock-up agreement. The representatives of the underwriters may, in their sole discretion and at any time without notice, release all or any portion of the shares subject to the lock-up agreements.

Use of Proceeds

Penterra Pharmaceuticals Corp. will not receive any of the proceeds from the sale of shares of common stock by the selling stockholders in this offering. All of the net proceeds from the sale of shares of common stock offered hereby will be received by the selling stockholders. The selling stockholders will bear all underwriting discounts and commissions and transfer taxes, if any, attributable to their sale of shares of common stock. The Company will bear all other costs, fees and expenses incurred in effecting the registration of the shares of common stock covered by this offering, including, without limitation, all registration and filing fees, Nasdaq listing fees, and fees and expenses of counsel and accountants for the Company.

Listing

The shares of common stock of Penterra Pharmaceuticals Corp. are listed on the Nasdaq Global Select Market under the ticker symbol "PNTR." On October 12, 2023, the last reported sale price of the shares of common stock on the Nasdaq Global Select Market was $42.17 per share.

Registration Statement Reference and Additional Information

The shares of common stock offered hereby have been registered under the Securities Act of 1933, as amended, pursuant to Registration Statement No. 333-274851 on Form S-3 (CIK: 0001987654), which was declared effective by the Securities and Exchange Commission on August 22, 2023. A prospectus supplement relating to this offering is being filed (or will be filed) with the SEC pursuant to Rule 424(b)(5) under the Securities Act of 1933, as amended.

This free writing prospectus does not contain all of the information that is required to be included in the registration statement and the related prospectus supplement. Investors and prospective investors are urged to read the complete Preliminary Prospectus Supplement dated October 2, 2023, the Base Prospectus, and the documents incorporated by reference therein, as the same may be amended or supplemented from time to time, for more complete information about the Company and this offering, including risk factors, use of proceeds, and financial statements. This free writing prospectus should be read in conjunction with, and is qualified in its entirety by reference to, the Preliminary Prospectus Supplement and the Base Prospectus.

Any information in this pricing term sheet that is inconsistent with information contained in the Preliminary Prospectus Supplement shall be deemed to modify and supersede the information in the Preliminary Prospectus Supplement. All other terms of the offering are as set forth in the Preliminary Prospectus Supplement.

Forward-Looking Statements

This free writing prospectus and the documents incorporated by reference herein and therein may contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These forward-looking statements are based on the Company's current expectations, estimates, forecasts and projections about the industry in which the Company operates and the beliefs and assumptions of the Company's management. Words such as "expects," "anticipates," "targets," "goals," "projects," "intends," "plans," "believes," "seeks," "estimates," "continues," "endeavors," "strives," "may," variations of such words, and similar expressions are intended to identify such forward-looking statements. In addition, any statements that refer to projections of the Company's future financial performance, the Company's anticipated growth and trends in its business, and other characterizations of future events or circumstances are forward-looking statements.

Readers are cautioned that these forward-looking statements are only predictions and are subject to risks, uncertainties and assumptions that are difficult to predict, including those identified in the "Risk Factors" section of the Preliminary Prospectus Supplement and the Base Prospectus and in the Company's most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q filed with the SEC. Therefore, actual results may differ materially and adversely from those expressed in any forward-looking statements. The Company undertakes no obligation to revise or update any forward-looking statements for any reason, except as required by applicable law.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this free writing prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This communication is not an offer to sell or the solicitation of an offer to buy any securities in any jurisdiction where such offer or solicitation would be unlawful.

The date of this Issuer Free Writing Prospectus is October 12, 2023.

Issuer:	Penterra Pharmaceuticals Corp.
Ticker / Exchange:	PNTR / Nasdaq Global Select Market
CUSIP:	70831X 10 5
Par Value:	$0.001 per share
Security:	Common Stock, par value $0.001 per share
Shares Offered (Base Offering):	6,250,000 shares
Over-Allotment Option:	Up to an additional 937,500 shares (representing 15% of the base offering), exercisable by the underwriters within 30 days of the pricing date (i.e., through and including November 11, 2023)
Total Shares (if over-allotment fully exercised):	7,187,500 shares
Selling Stockholders:	Dr. Elena Castellano, Dr. Riccardo Castellano, Dr. Marco Castellano, and Castellano Family Holdings LLC
Public Offering Price per Share:	$41.60
Underwriting discount per Share:	$1.04 (2.50% of public offering price)
Net Proceeds to Selling Stockholders per Share (before expenses):	$40.56
Aggregate Public Offering Price (Base Offering):	$260,000,000
Aggregate Underwriting discount (Base Offering):	$6,500,000
Aggregate Net Proceeds to Selling Stockholders (Base Offering, before expenses):	$253,500,000
Pricing Date:	October 12, 2023
Trade Date:	October 12, 2023
Expected Settlement Date:	October 17, 2023 (T+3)
Selling Stockholder	Shares Offered (Base)	Over-Allotment Shares	Total Shares (if fully exercised)
Dr. Elena Castellano	3,000,000	450,000	3,450,000
Dr. Riccardo Castellano	2,500,000	375,000	2,875,000
Dr. Marco Castellano	500,000	75,000	575,000
Castellano Family Holdings LLC	250,000	37,500	287,500
Total	6,250,000	937,500	7,187,500
Underwriter	Number of Base Shares

Ridgeline Securities LLC	2,812,500
Broadmark Capital Inc.	1,875,000
Linden Groves & Co.	937,500
Harborview Partners LLC	625,000
Total	6,250,000

CONFIDENTIAL — FOR PROSPECTIVE INVESTORS ONLY
ISSUER FREE WRITING PROSPECTUS
Filed Pursuant to Rule 433
Registration Statement No. 333-274851 (Form S-3)
Supplementing the Preliminary Prospectus Supplement dated October 2, 2023 and the accompanying Base Prospectus
October 12, 2023
Penterra Pharmaceuticals Corp.
Pricing Term Sheet
The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling Ridgeline Securities LLC toll-free at 1-800-555-0147 or Broadmark Capital Inc. toll-free at 1-800-555-0263.
Offering Overview
This pricing term sheet sets forth the final terms of the offering of shares of common stock of Penterra Pharmaceuticals Corp. ("Penterra" or the "Company") by the selling stockholders named in the prospectus supplement and should be read together with the preliminary prospectus supplement dated October 2, 2023 (the "Preliminary Prospectus Supplement") and the accompanying base prospectus (the "Base Prospectus") forming part of Registration Statement No. 333-274851. This term sheet supersedes and replaces in their entirety the estimated and indicative terms set forth in the Preliminary Prospectus Supplement to the extent inconsistent herewith.
Penterra Pharmaceuticals Corp. is not selling any shares in connection with this offering and will not receive any proceeds from the sale of shares of common stock by the selling stockholders. All shares of common stock being offered are being sold by the selling stockholders identified below.
The information in this pricing term sheet reflects the final pricing of the offering, which was determined after the close of trading on October 12, 2023 through a process of negotiations among the selling stockholders and the representatives of the underwriters.
Final Pricing Terms
Issuer Information.
Offering Terms.
Pricing.
The underwriting discount set forth above does not reflect any reimbursement of expenses of the underwriters by the selling stockholders. The selling stockholders have agreed to reimburse the underwriters for certain of their out-of-pocket expenses, including FINRA counsel fees, in an amount not to exceed $50,000 in the aggregate.
Key Dates.
Settlement of the shares of common stock is expected to occur on October 17, 2023, which will be the third business day following the date of pricing and the trade date. Under Rule 15c6-1 under the Securities Exchange Act of 1934, as amended, trades in the secondary market are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade shares of common stock prior to the delivery date may be required, by virtue of the fact that the shares initially will settle in T+3, to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement. Purchasers of shares of common stock who wish to make such trades should consult their own advisors.
Selling Stockholder Share Breakdown
The following table sets forth the number of shares of common stock to be sold by each selling stockholder in the base offering and the number of additional shares that each selling stockholder has granted the underwriters the option to purchase pursuant to the over-allotment option:
The over-allotment shares to be sold by each selling stockholder, if any, are proportionate to each selling stockholder's share of the base offering. The underwriters may exercise the over-allotment option in whole or in part, on one or more occasions, on or before November 11, 2023.
Underwriter Allocation. The following table sets forth the number of shares of common stock that each underwriter has severally agreed to purchase from the selling stockholders in the base offering:
Ridgeline Securities LLC and Broadmark Capital Inc. are acting as joint book-running managers for the offering. Linden Groves & Co. and Harborview Partners LLC are acting as co-managers for the offering. The underwriters are severally, and not jointly, obligated to purchase the number of shares set forth opposite their names above, subject to the conditions set forth in the underwriting agreement among the selling stockholders and the underwriters.
Each underwriter's proportionate share of the over-allotment option, if exercised, will be in the same proportion as the number of base shares set forth opposite such underwriter's name above bears to the total number of base shares.
Lock-Up Provisions
Each of the selling stockholders has agreed, subject to certain customary exceptions, that during the period beginning on the closing date of this offering (expected to be October 17, 2023) and ending 90 days thereafter (i.e., on January 15, 2024) (the "Lock-Up Period"), such selling stockholder will not, without the prior written consent of Ridgeline Securities LLC and Broadmark Capital Inc., as representatives of the underwriters:
(a) offer, pledge, announce the intention to sell, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, or otherwise transfer or dispose of, directly or indirectly, any shares of common stock of the Company or any securities convertible into or exercisable or exchangeable for shares of common stock of the Company that are owned or controlled by such selling stockholder following the closing of this offering;
(b) enter into any swap, hedge, or other arrangement that transfers, in whole or in part, any of the economic consequences of ownership of common stock of the Company, whether any such transaction described in clause (a) above or this clause (b) is to be settled by delivery of shares of common stock of the Company, in cash or otherwise; or
(c) make any demand for, or exercise any right with respect to, the registration of any shares of common stock of the Company or any security convertible into or exercisable or exchangeable for common stock of the Company.
The foregoing restrictions are subject to customary exceptions, including, without limitation, transfers of shares as bona fide gifts to immediate family members or to trusts for the benefit of immediate family members, transfers by will or intestacy, distributions by Castellano Family Holdings LLC to its members, and transfers to any affiliate of the selling stockholder, provided in each case that the transferee agrees in writing to be bound by the terms of the lock-up agreement. The representatives of the underwriters may, in their sole discretion and at any time without notice, release all or any portion of the shares subject to the lock-up agreements.
Use of Proceeds
Penterra Pharmaceuticals Corp. will not receive any of the proceeds from the sale of shares of common stock by the selling stockholders in this offering. All of the net proceeds from the sale of shares of common stock offered hereby will be received by the selling stockholders. The selling stockholders will bear all underwriting discounts and commissions and transfer taxes, if any, attributable to their sale of shares of common stock. The Company will bear all other costs, fees and expenses incurred in effecting the registration of the shares of common stock covered by this offering, including, without limitation, all registration and filing fees, Nasdaq listing fees, and fees and expenses of counsel and accountants for the Company.
Listing
The shares of common stock of Penterra Pharmaceuticals Corp. are listed on the Nasdaq Global Select Market under the ticker symbol "PNTR." On October 12, 2023, the last reported sale price of the shares of common stock on the Nasdaq Global Select Market was $42.17 per share.
Registration Statement Reference and Additional Information
The shares of common stock offered hereby have been registered under the Securities Act of 1933, as amended, pursuant to Registration Statement No. 333-274851 on Form S-3 (CIK: 0001987654), which was declared effective by the Securities and Exchange Commission on August 22, 2023. A prospectus supplement relating to this offering is being filed (or will be filed) with the SEC pursuant to Rule 424(b)(5) under the Securities Act of 1933, as amended.
This free writing prospectus does not contain all of the information that is required to be included in the registration statement and the related prospectus supplement. Investors and prospective investors are urged to read the complete Preliminary Prospectus Supplement dated October 2, 2023, the Base Prospectus, and the documents incorporated by reference therein, as the same may be amended or supplemented from time to time, for more complete information about the Company and this offering, including risk factors, use of proceeds, and financial statements. This free writing prospectus should be read in conjunction with, and is qualified in its entirety by reference to, the Preliminary Prospectus Supplement and the Base Prospectus.
Any information in this pricing term sheet that is inconsistent with information contained in the Preliminary Prospectus Supplement shall be deemed to modify and supersede the information in the Preliminary Prospectus Supplement. All other terms of the offering are as set forth in the Preliminary Prospectus Supplement.
Forward-Looking Statements
This free writing prospectus and the documents incorporated by reference herein and therein may contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These forward-looking statements are based on the Company's current expectations, estimates, forecasts and projections about the industry in which the Company operates and the beliefs and assumptions of the Company's management. Words such as "expects," "anticipates," "targets," "goals," "projects," "intends," "plans," "believes," "seeks," "estimates," "continues," "endeavors," "strives," "may," variations of such words, and similar expressions are intended to identify such forward-looking statements. In addition, any statements that refer to projections of the Company's future financial performance, the Company's anticipated growth and trends in its business, and other characterizations of future events or circumstances are forward-looking statements.
Readers are cautioned that these forward-looking statements are only predictions and are subject to risks, uncertainties and assumptions that are difficult to predict, including those identified in the "Risk Factors" section of the Preliminary Prospectus Supplement and the Base Prospectus and in the Company's most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q filed with the SEC. Therefore, actual results may differ materially and adversely from those expressed in any forward-looking statements. The Company undertakes no obligation to revise or update any forward-looking statements for any reason, except as required by applicable law.
Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this free writing prospectus is truthful or complete. Any representation to the contrary is a criminal offense.
This communication is not an offer to sell or the solicitation of an offer to buy any securities in any jurisdiction where such offer or solicitation would be unlawful.
The date of this Issuer Free Writing Prospectus is October 12, 2023.
Issuer: | Penterra Pharmaceuticals Corp.
Ticker / Exchange: | PNTR / Nasdaq Global Select Market
CUSIP: | 70831X 10 5
Par Value: | $0.001 per share
Security: | Common Stock, par value $0.001 per share
Shares Offered (Base Offering): | 6,250,000 shares
Over-Allotment Option: | Up to an additional 937,500 shares (representing 15% of the base offering), exercisable by the underwriters within 30 days of the pricing date (i.e., through and including November 11, 2023)
Total Shares (if over-allotment fully exercised): | 7,187,500 shares
Selling Stockholders: | Dr. Elena Castellano, Dr. Riccardo Castellano, Dr. Marco Castellano, and Castellano Family Holdings LLC
Public Offering Price per Share: | $41.60
Underwriting discount per Share: | $1.04 (2.50% of public offering price)
Net Proceeds to Selling Stockholders per Share (before expenses): | $40.56
Aggregate Public Offering Price (Base Offering): | $260,000,000
Aggregate Underwriting discount (Base Offering): | $6,500,000
Aggregate Net Proceeds to Selling Stockholders (Base Offering, before expenses): | $253,500,000
Pricing Date: | October 12, 2023
Trade Date: | October 12, 2023
Expected Settlement Date: | October 17, 2023 (T+3)
Selling Stockholder | Shares Offered (Base) | Over-Allotment Shares | Total Shares (if fully exercised)
Dr. Elena Castellano | 3,000,000 | 450,000 | 3,450,000
Dr. Riccardo Castellano | 2,500,000 | 375,000 | 2,875,000
Dr. Marco Castellano | 500,000 | 75,000 | 575,000
Castellano Family Holdings LLC | 250,000 | 37,500 | 287,500
Total | 6,250,000 | 937,500 | 7,187,500
Underwriter | Number of Base Shares
Ridgeline Securities LLC | 2,812,500
Broadmark Capital Inc. | 1,875,000
Linden Groves & Co. | 937,500
Harborview Partners LLC | 625,000
Total | 6,250,000

CONFIDENTIAL — FOR PROSPECTIVE INVESTORS ONLY

ISSUER FREE WRITING PROSPECTUS

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