Vice Chancellor Rennie’s memorandum opinion (by designation) in Shareholder Representative Services LLC v. Astellas Pharma Inc., C.A. No. 2023-0952-SKR (Del. Ch. Mar. 31, 2026) serves as a cautionary tale about the critical importance of precise contractual definitions in pharmaceutical acquisitions — particularly when over $100 million in milestone payments hinges on the meaning of a single clinical development term.

Background

In 2015, Potenza Therapeutics, Inc., a developer of immuno-oncology therapies, entered into a Collaboration Agreement and a Warrant Purchase Agreement (“WPA”) with Astellas Pharma Inc. The collaboration produced three experimental cancer drug candidates: ASP8374, ASP1948, and ASP1951. In December 2018, Astellas exercised its warrant option and acquired Potenza for an upfront payment of $164.4 million. The WPA also provided for contingent milestone payments tied to the clinical development of these compounds, including an $80 million payment upon initiation of the first Phase II Clinical Trial of any development product, and a $35 million payment upon initiation of the first Phase II Clinical Trial of a different development product.

Shareholder Representative Services LLC (“SRS”), acting on behalf of the former Potenza stockholders, brought this action after Astellas declined to make the $115 million in combined milestone payments. SRS argued that certain expansion cohorts within Astellas’s nominally “Phase 1b” clinical trials had effectively crossed the threshold into Phase II under the WPA’s definition. Astellas maintained that no Phase II Clinical Trial was ever initiated before the studies were terminated.

The Court’s Analysis

Vice Chancellor Rennie granted Astellas’s motion for summary judgment on the milestone payment claims but denied it as to a separate bad faith claim — resulting in a mixed ruling that leaves significant issues for trial.

On the milestone question, the Court’s analysis turned on the specific language the parties had negotiated. The WPA defined a Phase II Clinical Trial as a study designed to evaluate a development product’s safety and preliminary efficacy for patients with “the disease or condition” under study. As I have discussed in prior posts, the Court of Chancery consistently holds sophisticated parties to the plain meaning of the contractual language they chose. Here, the Court found that the definite article “the” and the singular “disease or condition” required a study focused on one specific disease. Because each of the relevant trials enrolled patients across multiple cancer types — including head and neck cancer, lung cancer, prostate cancer, ovarian cancer, and others — none satisfied the WPA’s definition. Accordingly, no Phase II Clinical Trial was ever initiated and the milestone payments were never triggered.

The Court also addressed a significant statute of limitations defense. Applying a three-year limitations period, the Court found that even under SRS’s own theory — that the milestones were triggered when Astellas began dosing patients in expansion cohorts using a Bayesian Optimal Phase 2 statistical design — the claims accrued no later than November 2019, well before SRS filed suit in September 2023. The Court found, however, that a triable issue of fact remains as to whether equitable tolling applies, based in part on Astellas’s January 2020 representation to SRS that no milestones had been achieved and that a “global Phase 1 study” was ongoing.

Finally, the Court denied summary judgment on SRS’s claim under Section 3.4(d) of the WPA, which required Astellas to act in good faith and use commercially reasonable efforts to achieve the milestones, and to refrain from taking any action in bad faith to prevent their achievement. The Court found it plausible that the trials were designed to avoid triggering Phase II milestones in cases where the products did not progress to Phase III. This claim survives for trial, subject to SRS’s ability to establish equitable tolling.

Key Takeaways

This decision carries important lessons for dealmakers in the life sciences space. First, it highlights the enormous financial consequences that can flow from the precise drafting of milestone definitions. The difference between a $115 million payout and no payout turned on the contractual meaning of “the disease or condition” — a phrase that could easily be overlooked in negotiation. Second, the survival of the bad faith claim is a reminder that even precisely drafted milestone definitions may not insulate a buyer from liability if the buyer is found to have deliberately structured its clinical program to avoid triggering payment obligations. For practitioners advising clients in pharmaceutical acquisitions, the case underscores the need both to draft milestone definitions with exacting precision and to ensure that good faith covenants adequately protect sellers against strategic avoidance.