Dr. Neeraj Agarwal and Dr. Jeanny Aragon-Ching discuss important advances in the treatment of prostate, bladder, and kidney cancers that were presented at the 2025 ASCO Annual Meeting.

TRANSCRIPT

Dr. Neeraj Agarwal: Hello, and welcome to the ASCO Daily News Podcast. I am Dr. Neeraj Agarwal, your guest host of the ASCO Daily News Podcast today. I am the director of the Genitourinary Oncology Program and a professor of medicine at the University of Utah Huntsman Cancer Institute and editor-in-chief of the ASCO Daily News.

I am delighted to be joined by Dr. Jeanny Aragon-Ching, a GU medical oncologist and the clinical program director of the GU Center at the Inova Schar Cancer Institute in Virginia. Today, we will be discussing some key abstracts in GU oncology that were presented at the 2025 ASCO Annual Meeting.

Our full disclosures are available in the transcript of this episode.

Jeanny, it is great to have you on the podcast.

Dr. Jeanny Aragon-Ching: Oh, thank you so much, Neeraj.

Dr. Neeraj Agarwal: Jeanny, let's begin with some prostate cancer abstracts. Let's begin with Abstract 5017 titled, “Phase 1 study results of JNJ-78278343 (pasritamig) in metastatic castration-resistant prostate cancer.” Can you walk us through the design and the key findings of this first-in-human trial?

Dr. Jeanny Aragon-Ching: Yeah, absolutely, Neeraj. So this study, presented by Dr. Capucine Baldini, introduces pasritamig, a first-in-class T-cell redirecting bispecific antibody that simultaneously binds KLK2 on prostate cancer cells and CD3 receptor complexes on T cells. KLK2 is also known as human kallikrein 2, which is selectively expressed in prostate tissue. And for reference, KLK3 is what we now know as the PSA, prostate-specific antigen, therefore making it an attractive and specific target for therapeutic engagement.

Now, while this was an early, first-in-human, phase 1 study, it enrolled 174 heavily pretreated metastatic CRPC patients. So many were previously treated with ARPIs, taxanes, and radioligand therapy. So given the phase 1 nature of this study, the primary objective was to determine the safety and the RP2D, which is the recommended phase 2 dose. Secondary objectives included preliminary assessment of antitumor activity.

So, pasritamig was generally well tolerated. There were no treatment-related deaths. Serious adverse events were rare. And in the RP2D safety cohort, where patients received the step-up dosing up to 300 mg of IV every 6 weeks, the most common treatment-related adverse events were low-grade infusion reactions. There was fatigue and grade 1 cytokine release syndrome, what we call CRS. And no cases of neurotoxicity, or what we call ICANS, the immune effector cell-associated neurotoxicity syndrome, reported. Importantly, the CRS occurred in just about 8.9% of patients. All were grade 1. No patients required tocilizumab or discontinued treatment due to adverse events. So, this suggests a favorable safety profile, allowing hopefully for outpatient administration without hospitalization, which will be very important when we're thinking about bispecifics moving forward.

In terms of efficacy, pasritamig showed promising activity. About 42.4% of evaluable patients achieved a PSA50 response. Radiographic PFS was about 6.8 months. And among patients with measurable disease, the objective response rate was about 16.1% in those with lymph node or bone metastases, and about 3.7% in those with visceral disease, with a median duration of response of about 11.3 months. So, altogether, this data suggests that pasritamig may offer a well-tolerated and active new potential option for patients with metastatic CRPC. Again, as a reminder, with the caveat that this is still an early phase 1 study.

Dr. Neeraj Agarwal: Thank you, Jeanny. These are promising results for a bispecific T-cell engager, pasritamig, in prostate cancer. I agree, the safety and durability observed here stand out, and this opens the door for further development, possibly even in earlier disease settings.

So, shifting now from immunotherapy to the evolving role of genomics in prostate cancer. So let's discuss Abstract 5094, a real-world, retrospective analysis exploring the prognostic impact of homologous recombination repair gene mutations, especially BRCA1 and BRCA2 mutations, in metastatic hormone-sensitive prostate cancer. Can you tell us more about this abstract, Jeanny?

Dr. Jeanny Aragon-Ching: Sure, Neeraj. So this study was presented by Dr. David Olmos, represents one of the largest real-world analyses we have evaluating the impact of homologous recombination repair, or what we would call HRR, alterations in metastatic hormone-sensitive prostate cancer. So, this cohort included 556 men who underwent paired germline and somatic testing. Now, about 30% of patients had HRR alterations, with about 12% harboring BRCA1 or BRCA2 mutations and 16% having alterations in other HRR genes. Importantly, patients were stratified via CHAARTED disease volume, and outcomes were examined across treatment approaches, including ADT alone, doublet therapy, and triplet therapy. The prevalence of BRCA and HRR alterations were about similar between the metastatic hormone-sensitive prostate cancer and the metastatic castrate-resistant prostate cancer, with no differences observed, actually, between the patients with high volume versus low volume disease.

So, the key finding was that BRCA and HRR alterations were associated with poor clinical outcomes in metastatic hormone-sensitive prostate cancer. And notably, the impact of these alterations may actually be even greater in metastatic hormone-sensitive prostate cancer than previously reported in metastatic CRPC. So, the data showed that when BRCA mutations are present, the impact of the volume of disease is actually limited. So, poor outcomes were observed across the board for both high-volume and low-volume groups. So, the analysis showed that patients with HRR alterations had significantly worse outcomes compared to patients without HRR alterations. Median radiographic progression-free survival was about 20.5 months for the HRR-altered patients versus 30.6 months for the non-HRR patients, with a hazard ratio of 1.6. Median overall survival was 39 months for HRR-altered patients compared to 55.7 months for the non-HRR patients, with a hazard ratio of 1.5. Similar significant differences were observed when BRCA-mutant patients were compared with patients harboring non-BRCA HRR mutations. Overall, poor outcomes were independent of treatment of ARPI or taxanes.

Dr. Neeraj Agarwal: Thank you, Jeanny. So, these data reinforce homologous recombination repair mutations as both a predictive and prognostic biomarker, not only in the mCRPC, but also in the metastatic hormone-sensitive setting as well. It also makes a strong case for incorporating genomic testing early in the disease course and not waiting until our patients have castration-resistant disease.

Dr. Jeanny Aragon-Ching: Absolutely, Neeraj. And I think this really brings home the point and the lead up to the AMPLITUDE trial, which is LBA5006, a phase 3 trial that builds on this very concept of testing with a PARP inhibitor, niraparib, in the hormone-sensitive space. Can you tell us a little bit more about this abstract, Neeraj?

Dr. Neeraj Agarwal: Sure. So, the AMPLITUDE trial, a phase 3 trial presented by Dr. Gerhardt Attard, enrolled 696 patients with metastatic hormone-sensitive prostate cancer and HRR gene alterations. 56% of these patients had BRCA1 and BRCA2 mutations. Patients were randomized to receive abiraterone with or without niraparib, a PARP inhibitor. The majority of patients, 78% of these patients, had high-volume metastatic hormone-sensitive prostate cancer, and 87% of these patients had de novo metastatic HSPC. And 16% of these patients received prior docetaxel, which was allowed in the clinical trial.

So, with a median follow-up of nearly 31 months, radiographic progression-free survival was significantly prolonged with the niraparib plus abiraterone combination, and median was not reached in this arm, compared to abiraterone alone, which was 29.5 months, with a hazard ratio of 0.63, translating to a 37% reduction in risk of progression or death. This benefit was even more pronounced in the BRCA1 and BRCA2 subgroup, with a 48% reduction in risk of progression, with a hazard ratio of 0.52. Time to symptomatic progression also improved significantly across all patients, including patients with BRCA1, BRCA2, and HRR mutations. Although overall survival data remain immature, early trends favored the niraparib plus abiraterone combination. The safety profile was consistent with prior PARP inhibitor studies, with grade 3 or higher anemia and hypertension were more common but manageable. Treatment discontinuation due to adverse events remained low at 11%, suggesting that timely dose modifications when our patients experience grade 3 side effects may allow o...