Ipsen has backed out of a $875 million deal for Sutro Biopharma’s ROR1-directed antibody-drug conjugate.
The deal, which was signed in April 2024, saw Ipsen agree to hand over $75 million in a combination of upfront payment and equity investment in return for STRO-003. The ADC targets the receptor tyrosine kinase-like orphan receptor 1 (ROR1) tumor antigen, which is overexpressed in various cancers—including solid tumors and blood cancers.
STRO-003 became the first ADC in Ipsen’s armory, although the French company wasted no time in adding a Topo1 inhibitor via a deal with Foreseen Biotechnology two months later.
According to Sutro’s own second-quarter earnings release Thursday, Ipsen has since had second thoughts about STRO-003. The Paris-based company “made a strategic decision not to advance the STRO-003 program … following the review of new data and developments in the ROR1 landscape,” Sutro explained.
Certainly the most recent data from the ROR1 space have been mixed. On the one hand, Merck & Co. posted phase 2 data on its own ROR1-directed ADC zilovertamab vedotin in lymphoma in May that evidenced the narrow safety and efficacy window for these drugs.
Specifically, Merck reported an overall response rate of 56.3% on the middle dose of 1.75 mg/kg, with little effect on response rate shown by increasing the dose. Meanwhile, three of the seven patients on the highest dose stopped taking the ADC because of adverse events, while the middle dose had a lower discontinuation rate.
Perhaps more worrying was an update in June about Lyell Immunopharma’s ROR1-targeted CAR-T cell therapy. Of 18 evaluable patients in a phase 1 solid tumor trial, four cases of grade 3 pneumonitis were reported, with one of these individuals dying of respiratory failure.
Lyell is still proceeding with the study but said at the time that it would vary the doses administered to different patients to account for this safety signal.
For its part, Sutro said in yesterday's release that STRO-003 “continues to be recognized as a well-engineered ADC candidate.” However, Sutro told Fierce this morning that the company has no plans to develop the drug internally.
The collapse of the deal with Ipsen means Sutro misses out on $800 million in combined development and commercial milestone payments. Still, Sutro said its cash runway won’t be impacted by Ipsen’s decision.
Sutro ended June with $205.1 million in the bank, which it expects to last until 2027. That estimate excludes any milestone from the company’s remaining partner Astellas, which is collaborating on two R&D programs for dual-payload immunostimulatory ADCs.
Sutro is also gearing up to take a crop of in-house therapies into the clinic, including a TF-targeting exatecan ADC and an integrin beta-6 ADC.