Anuradha Gopalan

Supplementary Figure S1 shows validation studies for the impact of PTEN loss on the NRG1 phenotype.

Supplementary Figure S2 shows the impact of NRG1 and HER2/3 inhibition on PTEN-loss prostate cancer in vivo.

Investigating the mechanisms of acquired resistance to antiandrogens remains a critical clinical need as patients with prostate cancer inevitably develop resistance to androgen receptor (AR)–targeted therapies. Previously, we demonstrated that neuregulin 1 (NRG1) derived from cancer-associated fibroblasts (CAF) promotes antiandrogen resistance through human epidermal growth factor receptor 3 (HER3)–AKT signaling. In this study, we sought to further dissect the molecular context in which NRG1-induced PI3K signaling activation plays a dominant role in driving resistance and evaluate whether targeting HER2/3 dimerization can influence sensitivity to AR inhibition. IHC analysis of radical prostatectomy specimens from patients with prostate cancer treated with or without neoadjuvant hormonal therapy shows that NRG1 was significantly upregulated following AR inhibition, independent of PTEN status. However, we found that stimulation with recombinant NRG1 or CAF-conditioned media induced resistance to AR inhibition only in PTEN wild-type prostate cancer cells and not in PTEN-deficient cells. Selective inhibition of NRG1 using the clinical-grade bispecific humanized immunoglobulin G1, zenocutuzumab (Zeno, MCLA-128), restored sensitivity to AR-targeted therapies in PTEN wild-type tumors, demonstrating its efficacy as a potential therapeutic agent to block the effects of NRG1. In the context of PTEN loss and AR inhibitor resistance, Zeno did not restore sensitivity. These findings highlight the critical molecular context in which tumor microenvironment–derived NRG1 affects responsiveness to AR inhibition and suggest that targeting NRG1 is a promising strategy for overcoming resistance to androgen blockade in PTEN wild-type prostate cancers.

Supplementary Table 3. Summary of Grade 3 to 5 Treatment-emergent Adverse Events

Supplementary Table 1. Representativeness of Study Participants

Supplementary Figure S3. Mutational Profile by Cohort and Treatment Group. Distribution of key genomic alterations among patients with metastatic prostate cancer. (Left) Comparison of alteration frequencies between Cohort A and Cohort B. (Right) Comparison of alteration frequencies between treatment groups receiving Apa alone versus Apa + AAP. The most frequently altered genes included TP53, PTEN, SPOP, FOXA1, and AGO2.

Purpose:To accelerate prostate cancer drug development and identification of promising therapies, we aimed to establish a framework for a multimodal therapy (MMT) approach using intermediate endpoints of efficacy due to treatment.Patients and Methods:In the MetaCURE trial, patients with untreated, high-risk localized (cohort A) or low-volume metastatic (cohort B) disease were randomized 1:1 to apalutamide or apalutamide and abiraterone acetate plus prednisone and androgen deprivation therapy for 10 months. Cohort B also received stereotactic body radiotherapy (RT) at 4 months. All patients underwent a radical prostatectomy (6 months ± postoperative RT at 10 months). The primary endpoint was pathologic complete response (pCR; no residual tumor) or minimal residual disease (MRD; ≤5 mm residual carcinoma), and the secondary endpoint an undetectable PSA following testosterone (T) recovery (T ≥ 150 ng/dL) at 24 months.Results:A pCR or MRD was achieved in 4 [12%; 90% confidence interval (CI), 4%–26%] and 5 (15%; 90% CI, 6%–29%) patients in cohorts A and B, respectively. Undetectable PSA and T-recovery at 24 months occurred in 20 (61%; 95% CI, 42%–77%) patients in cohort A and 13 (39%; 95% CI, 23%–58%) patients in cohort B.Conclusions:MMT for newly diagnosed high-risk localized and low-volume metastatic prostate cancer is feasible, safe, and provides a rapid readout of efficacy. A significant proportion of patients, including those with oligometastatic disease, maintained an undetectable PSA following T-recovery at the 2-year endpoint. These results have informed the design of an adaptive trial using MMT on a continuous basis to prioritize effective approaches for further study.

Supplementary Figure S2. Time to Testosterone Recovery by Cohort and Treatment Assignment. Cumulative probability curves depict time to testosterone recover measured from the end of systemic therapy among participants in Cohort A (red) and Cohort B (blue). Solid lines represent participants treated with ADT + Apa, while dashed lines represent those receiving ADT + Apa + AAP. The number of participants at risk at each time point is shown below the graph.

Supplementary Figure S1 Time to Testosterone Recovery by Treatment Assignment Cumulative probability of serum testosterone recovery after completion of systemic therapy is shown for both treatment arms combined (solid orange line) and separately for participants receiving ADT + Apa or ADT + Apa + AAP (blue dashed line). Time was measured from the end of systemic therapy to testosterone recovery. Median time to recovery was similar between treatment arms. The table below the plot shows the number of participants at risk at each time point.

Supplementary Table 2. Pathologic Response By Patient (table continued on next page)