Pfizer deals another mesothelin blow

Not long after MediLink got an endorsement from Roche over its Tmalin ADC linker-payload technology, another Tmalin-based project has fallen by the wayside: PF-08052666, development of which had been led by Pfizer. After the recruitment target in the anti-mesothelin ADC’s phase 1 solid tumour trial was slashed from 365 to 19, and the study’s status changed from “recruiting” to “active, not recruiting” on clinicaltrials.gov, a spokesperson for Pfizer confirmed the asset had been discontinued for "business strategic reasons”. The decision wasn’t spurred by safety concerns, regulatory requests, or any conduct issues, the spokesperson added. The move looks more likely to be down to the target than the ADC technology: mesothelin has seen a litany of failures including, most recently, Zymeworks’ T-cell engager ZW171. PF-08052666’s removal leaves RemeGen’s RC88 as the only clinical-stage mesothelin-targeting ADC, according to OncologyPipeline – although there are several preclinical candidates in development. PF-08052666, also known as HBM9033, was originally developed by MediLink and Harbour BioMed; Pfizer licensed global rights in December 2023 for $53m up front. The next mesothelin readout could involve Context’s T-cell engager CT-95, which is set to yield phase 1 data in mid-2026.

Mesothelin-targeting ADCs in development

Note: *targets mesothelin × mesothelin; **targets mesothelin × FOLR1; ***targets mesothelin × MUC1. Source: OncologyPipeline.