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ABBV-969, a Dual-Targeted PSMA-STEAP1 ADC in Heavily Pretreated mCRPC - Tanya Dorff

June 18, 2026

Tanya Dorff presents phase 1 data on ABBV-969, a dual-targeting antibody-drug conjugate binding PSMA and STEAP1 to deliver a topoisomerase payload in 49 heavily pretreated mCRPC patients. over 80% of patientsof whom had received docetaxel and more than half had prior lutetium. Confirmed PSA50 response rate was approximately two-thirds, with a median duration of response around 11 months and RECIST objective response rate of 45%. Radiographic progression-free survival was approximately 15 months, compared to the typical three to six months in this population. Median duration on treatment was 299 days despite grade 3 anemia in approximately 45% of patients.

Biographies:

Tanya Dorff, MD, Medical Oncologist, Professor of Medicine, Vice Chair of Clinical Affairs, Department of Medical Oncology & Therapeutics Research, Division Chief of the Genitourinary Disease Program, City of Hope, Duarte, CA

Zachary Klaassen, MD, MSc, Urologic Oncologist, Assistant Professor of Surgery/Urology at the Medical College of Georgia at Augusta University, Wellstar MCG, Georgia Cancer Center, Augusta, GA


Related Content:

ASCO 2026: A Phase 1, First-in-Human Study Evaluating the Safe, Pharmacokinetics, and Efficacy of ABBV-969 in Patients with mCRPC

APCCC 2026: Beyond PSMA: New Theranostic Targets Approaching near Term Clinical Implementation

PSMA and Beyond 2025: Beyond PSMA in Prostate Cancer: STEAP1, DLL3, and CD46

Read the Full Video Transcript

Zachary Klaassen: Hi, my name is Zach Klaassen, urologic oncologist in Augusta, Georgia, and I'm delighted to be joined on UroToday at ASCO 2026 in Chicago with Dr. Tanya Dorff, who is a medical oncologist at City of Hope in California. Today, we'll be discussing Dr. Dorff's Phase 1 trial, ABBV-969, rapid oral presentation at ASCO.
Thanks so much for joining us on UroToday, Tanya.

Tanya Dorff: Yeah, great to be here.

Zachary Klaassen: So what is ABBV-969 and how does it fit into the prostate cancer landscape?

Tanya Dorff: Yeah, so this is a novel antibody drug conjugate, so what I like to call a smart chemo. And it's dual-targeted, so it's able to bind to either PSMA or STEAP1. So those are two proteins that we know are very commonly expressed in prostate cancer patients. And the antibody can internalize and deliver the topoisomerase payload when binding to either/or antigen. It doesn't have to bind to both.

Zachary Klaassen: I see. Okay. And Phase 1, so this is initial data. These are heavily pretreated patients. So maybe just walk us through what these patients look like and what the dosing looks like.

Tanya Dorff: Yeah. We're presenting on 49 patients who were treated in the dose-escalation. So these were patients who had progressed on an AR pathway inhibitor, and most had had two or three. They had progressed on a taxane. So 80-some percent had had docetaxel, a significant percentage had had cabazitaxel, and more than half had had lutetium-PSMA exposure.

Zachary Klaassen: Wow. So this is the patients that are really looking for something to continue optimizing quality of life, optimizing length of life. Some very impressive high-level results from your presentation. Maybe take our listeners through that.

Tanya Dorff: Yeah. So we were very encouraged by the confirmed PSA50 response rate, which was about two-thirds of patients
achieving that. But even more so to me is it's impressive how durable these responses were. So the median duration of response was around 11 months.

Zachary Klaassen: Wow.

Tanya Dorff: And then when you turn to RECIST objective response, so about 16% of patients had liver mets and another 15% or 16% with lung metastases, there were bone-only patients and the majority of patients had some kind of bone involvement, but the RECIST objective response rate of 45% I think is striking. And that did include patients with liver metastases. And then the radiographic progression-free survival being around 15 months.

Zachary Klaassen: Wow.

Tanya Dorff: So in this population, we're often seeing rPFS of three to six months, so I found that durability of response is really encouraging.

Zachary Klaassen: Yeah. Patients want to know that it works and how long, Doc, is it going to work for. And to think that's, especially as you said, in this population with really not a lot of options left, so to speak, this is fantastic.

What about tolerability? What'd you guys see in terms of adverse events?

Tanya Dorff: Yeah, so certainly there are toxicities. Even though it's a smart chemo, this is a chemo payload. And so we did see about 45% Grade 3 anemia. Now, the median hemoglobin at study entry was 10.9, so we're already starting low. And about a third of patients ended up needing dose holds or dose reductions, but the median duration on treatment was 299 days.

Zachary Klaassen: Wow.

Tanya Dorff: So to me, that speaks to tolerability. Yes, there were some GI toxicities, nausea, anorexia, yes, there's some myelosuppression, but with dose holding, dose modification, patients were able to continue to stay on treatment.

Zachary Klaassen: That's fantastic. Where does ABBV-969 go from here? What are the next steps for this targeted therapy?

Tanya Dorff: Well, it is interesting that this was a biomarker-unselected patient population, but obviously we would be interested in looking at the available data to look for expression levels and how that may correlate with response. We'll also be looking at toxicity as it relates to prior treatments in order to best try to position this agent within the therapeutic landscape for mCRPC.

But I think it's clear these efficacy results speak loudly that we need to continue development of this agent and that it may well be able to cross over that therapeutic hurdle of approval and become something we can use.

Zachary Klaassen: No, congratulations. Rapid oral presentation and this really unmet need in these heavily pretreated patients. Congrats and thank you for joining us on UroToday.

Tanya Dorff: Thanks so much.