Contract analysis

I. Executive Summary This memorandum summarizes the findings of Calderwood & Harkness LLP ("C&H") from its regulatory due diligence review of Caliston BioSciences, Inc. ("Caliston" or the "Company"), a privately held, Delaware-incorporated, clinical-stage biopharmaceutical company with principal offices at 88 Harbor Point Road, Cambridge, MA 02142. This memorandum has been prepared at the request of, and is addressed

II. Company Overview — Regulatory Profile Corporate Background. Caliston BioSciences, Inc. was founded in 2017 and is incorporated under the laws of the State of Delaware. The Company's Employer Identification Number is 84-4219063. Its registered agent is Pemberton Industries, 251 Little Falls Drive, Wilmington, DE 19808. Caliston's principal offices and laboratory facilities are located at 88 Harbor Point Road, Camb

III. IND Status — CLT-4019 (IND 158429) A. IND Filing and Acceptance Caliston filed an Investigational New Drug Application for CLT-4019 with the FDA's Center for Drug Evaluation and Research ("CDER"), Division of Oncology Products, in March 2020. The IND was assigned number 158429. The IND submission included a comprehensive package of preclinical data, including pharmacology and toxicology studies conducted in both

IV. Phase 2b Clinical Trial — CLT-4019 A. Trial Design The ongoing Phase 2b clinical trial of CLT-4019 is being conducted pursuant to Protocol CLT-4019-002 (as amended). Key design parameters of the trial are as follows: Indication. HR+/HER2– metastatic breast cancer in adult patients who have progressed on at least one prior line of endocrine-based therapy in the metastatic setting. Study Type. Phase 2b, multicenter

V. Preclinical Pipeline — CLT-5227 and CLT-6034 CLT-5227 CLT-5227 is a next-generation kinase inhibitor designed to target a differentiated kinase pathway implicated in non-small cell lung cancer ("NSCLC"). The compound is currently in late preclinical development. As described in the management presentation, Caliston has completed in vitro and in vivo proof-of-concept studies demonstrating anti-tumor activity in NSC

VI. Anticipated Regulatory Pathway to NDA Filing A. Phase 2b to Phase 3 Transition Potential Pathways. The regulatory pathway from Phase 2b to potential NDA approval for CLT-4019 will depend in significant part on the Phase 2b topline data expected in Q4 2023. Based on our discussions with Caliston management and our review of the regulatory strategy documents in the data room, Caliston has identified two principal p

VII. Change-of-Control Regulatory Considerations A. FDA Regulatory Impact of Change of Control IND Transfer. Under 21 C.F.R. § 312.70, when there is a change in the sponsor of an IND, the new sponsor must submit appropriate amendments to the IND to reflect the change. The transfer of IND sponsorship from Caliston to Penterra (or to a Penterra subsidiary, as applicable) upon consummation of the Transaction is a proced

VIII. Intellectual Property — Regulatory Exclusivity Considerations A comprehensive analysis of Caliston's intellectual property portfolio, including patent claims, prosecution history, freedom-to-operate, and third-party intellectual property risks, is set forth in the separate intellectual Property Diligence Memorandum dated July 21, 2023, prepared by C&H's intellectual property practice group. This Section VIII ad

IX. Risk Factors and Open Items A. Clinical Risk Phase 2b Topline Data Uncertainty. The most significant risk factor identified in this regulatory due diligence review is the inherent uncertainty associated with the Phase 2b topline data for CLT-4019, which are expected in Q4 2023 but are not yet available as of the date of this memorandum. The Transaction valuation of $925 million in base consideration, together wit