Contract analysis

I. INTRODUCTION AND TRANSACTION OVERVIEW This Closing Memorandum has been prepared by Calderwood & Harkness LLP ("C&H" or "Firm") to memorialize the closing mechanics and confirm the successful settlement of the registered selling-stockholder secondary offering (the "Offering") of shares of common stock of Penterra Pharmaceuticals Corp. ("Penterra," "PPC," or the "Company"). This memorandum is intended to serve as a

II. PARTIES A. Issuer. Penterra Pharmaceuticals Corp. is a corporation organized and existing under the laws of the State of Delaware. The Company's common stock is listed on The Nasdaq Global Select Market under the ticker symbol "PNTR." The Company's registered agent in Delaware is actionaltional Registered Agents Inc., located at 251 Little Falls Drive, Wilmington, DE 19808. The principal officers of the Company r

III. PRICING SUMMARY The pricing terms of the Offering were established on October 12, 2023 (the "Pricing Date") and are summarized below: The underwriting discount of 2.50% of the public offering price, or $1.04 per share, is consistent with market practice for registered secondary offerings of this size by selling stockholders. The aggregate underwriting commission for the base offering of 6,250,000 shares totals $

IV. UNDERWRITING COMMISSION ALLOCATION The total underwriting commission of $6,500,000 is allocated among the four underwriters in accordance with the terms of the Underwriting Agreement as follows: Reconciliation: The sum of the individual commission amounts is confirmed as follows: $2,925,000 + $1,950,000 + $975,000 + $650,000 = $6,500,000, which equals 6,250,000 shares multiplied by $1.04 per share. The commission

V. FUNDS FLOW A. Aggregate Funds Flow Summary The aggregate funds flow for the base offering is summarized below: Total Gross Proceeds (6,250,000 shares × $41.60): $260,000,000 Less: Total Underwriting discount (6,250,000 shares × $1.04): ($6,500,000) Net Proceeds Payable to Selling Stockholders: $253,500,000 B. Allocation of Net Proceeds Among Selling Stockholders The net proceeds of $253,500,000 are allocated among

1. The 6,250,000 shares of common stock were delivered by the selling stockholders (through Pinnacle Trust & Transfer Co. as custodian) via book-entry transfer through the facilities of DTC against payment of the aggregate gross proceeds.

2. Ridgeline Securities LLC, in its capacity as representative of the several underwriters, received the aggregate gross proceeds of $260,000,000 through DTC's delivery-versus-payment settlement system.

3. The underwriters retained the aggregate underwriting discount of $6,500,000 from the gross proceeds, allocated among the underwriters in accordance with the percentages set forth in Section IV above.

4. The remaining net proceeds of $253,500,000 were wire-transferred by Ridgeline Securities LLC to the selling stockholders (or their designated bank accounts) in accordance with wire instructions provided under the Power of Attorney and Custody Agreement dated October 12, 2023. David Orenstein, in his capacity as attorney-in-fact for the selling stockholders pursuant to the Power of Attorney and Custody Agreement, c

5. Wire transfers to each selling stockholder's designated account were confirmed as completed on October 17, 2023, with the specific amounts set forth in the allocation table in Section V.B above. D. Issuer Expenses Although the Company is not selling shares and is not receiving any proceeds from the Offering, the Company agreed to bear all offering expenses other than the underwriting discount (which is borne by th

VI. SETTLEMENT MECHANICS Settlement of the base offering was effected through the facilities of The Depository Trust Company ("DTC") on October 17, 2023, the Closing Date, which was the third business day following the Trade Date of October 12, 2023 (T+3), in accordance with Rule 15c6-1 under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). The settlement process was coordinated among the transfe

VII. LOCK-UP WAIVER AND NEW LOCK-UP A. IPO Lock-Up Waiver In connection with the Company's initial public offering, which closed on April 17, 2023, each of the selling stockholders entered into 180-day lock-up agreements (the "IPO Lock-Up Agreements") restricting the sale, transfer, or other disposition of their shares of common stock for a period of 180 calendar days following the closing of the IPO. The original lo

VIII. CONDITIONS PRECEDENT — CONFIRMATION OF SATISFACTION A. Underwriting Agreement Conditions All conditions precedent to the obligations of the underwriters to close the purchase of the shares, as set forth in the Underwriting Agreement dated October 12, 2023, were satisfied or waived as of the Closing on October 17, 2023. Calderwood & Harkness LLP, in its capacity as issuer's counsel, coordinated with Caldwell, Pe

1. Officer's Certificate of Penterra. An Officer's Certificate of Penterra Pharmaceuticals Corp. dated October 17, 2023, signed by Dr. Marco Castellano in his capacity as Chief Executive Officer and Lisa Hargrove in her capacity as Chief Financial Officer. The Officer's Certificate certified: (i) the accuracy of the Company's representations and warranties set forth in the Underwriting Agreement as of the Closing Dat

2. Secretary's Certificate of Penterra. A Secretary's Certificate of Penterra Pharmaceuticals Corp. dated October 17, 2023, signed by David Orenstein in his capacity as General Counsel and Corporate Secretary. The Secretary's Certificate certified: (i) the incumbency and signatures of the officers of the Company authorized to execute the Underwriting Agreement and other transaction documents; (ii) that attached there

3. Good Standing Certificate. A Certificate of Good Standing for Penterra Pharmaceuticals Corp. issued by the Secretary of State of the State of Delaware dated October 16, 2023, confirming that the Company is in good standing under the laws of the State of Delaware.

4. Issuer's Counsel Legal Opinion. A legal opinion of Calderwood & Harkness LLP dated October 17, 2023, addressed to the underwriters, opining on the following matters: (i) the 6,250,000 shares of common stock being sold in the Offering have been duly authorized and are validly issued, fully paid, and non-assessable; (ii) the Company has been duly incorporated and is validly existing and in good standing under the la

5. Issuer's Counsel Negative Assurance Letter (10b-5 Letter). A negative assurance letter (commonly referred to as a "10b-5 letter") of Calderwood & Harkness LLP dated October 17, 2023, addressed to the underwriters. The negative assurance letter stated that, based upon C&H's participation in the preparation of the registration statement, the base prospectus, and the prospectus supplement, and its review of certain c

6. Comfort Letter of Graystone & Whitmore LLP. An initial comfort letter of Graystone & Whitmore LLP was delivered in connection with the filing of the preliminary prospectus supplement on October 2, 2023. A bring-down comfort letter of Graystone & Whitmore LLP dated October 17, 2023 was delivered on the Closing Date, confirming that: (i) no material changes had occurred since the date of the initial comfort letter;

7. Selling Stockholder Certificates. Certificates dated October 17, 2023, executed by each of the selling stockholders (or by David Orenstein as attorney-in-fact for the selling stockholders pursuant to the Power of Attorney and Custody Agreement) certifying that: (i) the representations and warranties of the selling stockholders set forth in the Underwriting Agreement and in the Selling Stockholder Representation Le

8. Lock-Up Waiver Consents. All three lock-up waiver consents from the IPO underwriters were received and confirmed, as described in detail in Section VII.A above: (i) Ridgeline Securities LLC (consent dated September 29, 2023, signed by Jonathan Pryce-Hall); (ii) Broadmark Capital Inc. (consent dated September 29, 2023, signed by Samuel Okonkwo); and (iii) Morningstar Zanthor & Co. (consent dated September 29, 2023,

9. New Lock-Up Agreements. Executed 90-day lock-up agreements (the Secondary Lock-Up Agreements) were received from each of the four selling stockholders, as described in detail in Section VII.B above. Each Secondary Lock-Up Agreement restricts the disposition of retained shares for 90 days from the Closing Date (through January 15, 2024).

10. Power of Attorney and Custody Agreement. The Power of Attorney and Custody Agreement dated October 12, 2023, executed by each selling stockholder, appointing David Orenstein as attorney-in-fact with authority to execute and deliver the Underwriting Agreement, closing certificates, and other transaction documents on behalf of the selling stockholders, and appointing Pinnacle Trust & Transfer Co. as custodian of th

11. Transfer Agent Direction Letter. A direction letter from Penterra Pharmaceuticals Corp. to Pinnacle Trust & Transfer Co. dated October 16, 2023, signed by David Orenstein on behalf of the Company, instructing the transfer agent to effect the book-entry delivery of 6,250,000 shares of common stock through the facilities of DTC on the Closing Date in connection with the settlement of the Offering.

12. Underwriting Agreement (Execution Version). The fully executed Underwriting Agreement dated October 12, 2023 was received, bearing the signatures of: (i) Penterra Pharmaceuticals Corp., by Lisa Hargrove, Chief Financial Officer; (ii) each of the four selling stockholders (Dr. Elena Castellano, Dr. Riccardo Castellano, Dr. Marco Castellano, and Castellano Family Holdings LLC, by David Orenstein as attorney-in-fact

13. Selling Stockholder Representation Letters. Selling Stockholder Representation Letters dated October 12, 2023, executed by each of the four selling stockholders (or by David Orenstein as attorney-in-fact). The representation letters contain representations and warranties by the selling stockholders with respect to: (i) beneficial ownership of the shares to be sold; (ii) authority to sell the shares (including the

IX. SEC FILINGS SUMMARY The following SEC filings were made in connection with the Offering: All filings were prepared or reviewed by Calderwood & Harkness LLP and were timely filed with the SEC via EDGAR through Apex Financial Printing Inc. The timely filing of the Section 16 Form 4s for the individual selling stockholders is being monitored as a post-closing matter (see Section XIII below).

X. OVER-ALLOTMENT OPTION STATUS In connection with the Offering, the selling stockholders granted the several underwriters a 30-day option (the "Over-Allotment Option") to purchase up to an additional 937,500 shares of common stock at the public offering price less the underwriting discount. The Over-Allotment Option was granted pursuant to Section 2 of the Underwriting Agreement and expires on November 11, 2023 (i.e

XI. POST-CLOSING OWNERSHIP SUMMARY The following table sets forth the ownership positions of the Castellano family selling stockholders immediately following the closing of the base offering on October 17, 2023. The total shares of common stock outstanding remain unchanged at 120,000,000 shares, as no primary shares were issued in connection with the Offering. The public float of the Company's common stock has increa

XII. KEY TIMELINE RECAP The following is a summary of the key dates and milestones in connection with the Offering:

XIII. OUTSTANDING ITEMS / POST-CLOSING MATTERS The following items remain outstanding as of the date of this memorandum and require monitoring or further action by the Calderwood & Harkness deal team:

1. Over-Allotment Option Monitoring. Calderwood & Harkness will continue to monitor the Over-Allotment Option exercise period through its expiration on November 11, 2023. If the Over-Allotment Option is exercised in whole or in part by the underwriters, Calderwood & Harkness will coordinate the preparation and delivery of additional closing deliverables for the over-allotment closing, which is expected to occur on or

2. Section 16 Form 4 Filings. The Section 16 Form 4 filings for the three individual selling stockholders who are Section 16 insiders — Dr. Elena Castellano (disposition of 3,000,000 shares), Dr. Riccardo Castellano (disposition of 2,500,000 shares), and Dr. Marco Castellano (disposition of 500,000 shares) — are due to be filed with the SEC within two business days of the Pricing Date (October 12, 2023). David Orenst

3. Closing Binder Compilation. Brendan Walsh will be responsible for the preparation and compilation of the closing binder, including the closing index and executed copies of all transaction documents and closing deliverables. Closing binder sets will be distributed to all parties in accordance with customary practice. The target completion date for the closing binder is October 27, 2023.

4. Lock-Up Compliance Monitoring. Calderwood & Harkness will monitor compliance with the new 90-day Secondary Lock-Up Agreements through the expiration date of January 15, 2024. Any requests for early release or transfer exceptions will be reviewed in consultation with the Representatives (Ridgeline Securities LLC and Broadmark Capital Inc.) and the Company.

5. Final Invoicing. Calderwood & Harkness will submit its final invoice under the capped fee arrangement of $485,000 (plus disbursements) upon the closing of the matter. If the Over-Allotment Option is exercised, the fee arrangement may be subject to adjustment as agreed with the Company. Final invoicing is expected upon matter close, currently anticipated for October 27, 2023 (absent over-allotment exercise).

XIV. DISTRIBUTION This Closing Memorandum is privileged and confidential and constitutes attorney work product. It is being distributed solely to the following individuals: Calderwood & Harkness LLP Deal Team: • Jennifer Kwon, Partner • Theodore Langston, Partner • Audrey Zhou, Senior Associate • Brendan Walsh, Associate Penterra Pharmaceuticals Corp. (as appropriate, subject to privilege considerations): • David Ore

Section 16 Form 4 Filings | Due within two business days of October 12, 2023 | Form 4 filings reporting the disposition of shares by the three individual selling stockholders who are Section 16 insiders: Dr. Elena Castellano (disposition of 3,000,000 shares), Dr. Riccardo Castellano (disposition of 2,500,000 shares), and Dr. Marco Castellano (disposition of 500,000 shares). Note: Castellano Family Holdings LLC may al