GU Cancers 2026 | Phase Ib trial of pasritamig, a bispecific BiTE, and docetaxel in mCRPC
David Wise, MD, PhD, NYU Langone Health, New York, NY, discusses initial results from a Phase Ib study (NCT05818683) evaluating the safety and efficacy of pasritamig, a first in class bispecific T-cell engager targeting KLK2 and CD3, combined with docetaxel in participants with metastatic castration-resistant prostate cancer (mCRPC). The combination demonstrated a promising anti-tumor activity and a manageable safety profile consistent with docetaxel monotherapy and no cytokine release syndrome. This interview took place at the 2026 ASCO GU Cancers Symposium in San Francisco, CA.
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Transcript
So another combination approach where we’re taking a next-generation immunotherapy and combining it with another standard of care agent. So some shared theme there. Pastoridomig, though, is different. It’s a bispecific T-cell engager. So it’s really not increasing clonality that we’re aware of. Rather, it’s bringing T-cells in a relatively unselected way to the tumor...
So another combination approach where we’re taking a next-generation immunotherapy and combining it with another standard of care agent. So some shared theme there. Pastoridomig, though, is different. It’s a bispecific T-cell engager. So it’s really not increasing clonality that we’re aware of. Rather, it’s bringing T-cells in a relatively unselected way to the tumor. And that’s been the problem with prostate cancer is how do you get T-cells into the tumor? And BITES are really starting to approach that in a successful way. The unique aspect of Pasteridomig is that the bispecific binds to KLK2 with CD3. And KLK2 is a newer target on the, I would say, landscape that is much more specific for luminal prostate adenocarcinoma cells. It really is not expressed in other non-prostate tissue essentially at all, as best as we can tell, which is very different from the other agents. And so it also gives quite a clean toxicity profile because of that. So we don’t see the same high grade CRS and that may also be due to the way it was dose optimized in the phase one. Here we report at this conference the combination data in terms of safety and efficacy in the phase one with docetaxel. And what we found is really a quite good consistent safety profile compared to what you’d expect with each agent as a monotherapy and what we didn’t find we continue to not find high-grade CRS thankfully with the combination and we found the same essential docetaxel toxicity you’d expect so it really didn’t seem to be much downside from a safety standpoint to adding this agent to docetaxel. And the efficacy data looked quite impressive in this phase one single arm trial where we saw, particularly if you highlight the taxane-naive patient population, remember these are MCRPC patients who all have progressed on at least one ARPI and often multiple other lines of therapy as well. But if you focus on the taxane-naive patient population, we saw an 88% PSA-50 response rate. And so that compares quite favorably to what you’d expect with docetaxel alone, which would be approximately 45%, and what you’d expect with the pasteuridomide, which is somewhere in the order of 30 to 35%.
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