Bipolar androgen therapy plus olaparib in men with metastatic castration-resistant prostate cancer

BACKGROUND

Bipolar androgen therapy (BAT) results in rapid fluctuation of testosterone (T) between near-castrate and supraphysiological levels and has shown promise in metastatic castration-resistant prostate cancer (mCRPC). Its clinical effects may be mediated through induction of DNA damage, and preclinical studies suggest synergy with PARP inhibitors.

PATIENTS AND METHODS

This was a single-center, Phase II trial testing olaparib plus BAT (T cypionate/enanthate 400 mg every 28 days) with ongoing androgen deprivation. Planned recruitment was 30 subjects (equal proportions with/without homologous recombination repair [HRR] gene mutations) with mCRPC post abiraterone and/or enzalutamide. The primary objective was to determine PSA50 response (PSA decline ≥50% from baseline) rate at 12-weeks. The primary analysis utilized the entire (intent-to-treat [ITT]) cohort, with those dropping out early counted as non-responders. Secondary/exploratory analyses were in those treated beyond 12-weeks (response-evaluable cohort).

RESULTS

Thirty-six patients enrolled and 6 discontinued prior to response assessment. In the ITT cohort, PSA50 response rate at 12-weeks was 11/36 (31%; 95% CI 17-48%), and 16/36 (44%, 95% CI 28-62%) had a PSA50 response at any time on-study. After a median follow-up of 19 months, the median clinical/radiographic progression-free survival in the ITT cohort was 13.0 months (95% CI 7-17). Clinical outcomes were similar regardless of HRR gene mutational status.

CONCLUSIONS

BAT plus olaparib is associated with high response rates and long PFS. Clinical benefit was observed regardless of HRR gene mutational status.

Pathological Effects of Apalutamide in Lower-risk Prostate Cancer: Results From a Phase II Clinical Trial

PURPOSE

Active surveillance is a safe and effective strategy for men with lower-risk prostate cancer who want to avoid local therapy; however, many patients on active surveillance progress to active treatment (eg, prostatectomy or radiation). We hypothesized that apalutamide would decrease active surveillance attrition rates through downstaging low-grade tumors.

MATERIALS AND METHODS

This was an open-label, single-arm, phase II study testing 90 days of oral apalutamide 240 mg daily in men with low- to intermediate-risk prostate cancer on active surveillance. The primary objective was to determine the percentage of patients with a negative biopsy immediately following treatment. Secondary objectives were to assess long-term clinical outcomes, quality of life, safety, and biomarkers of response/resistance.

RESULTS

Twenty-three patients enrolled and 22 completed 90 days of apalutamide with post-treatment biopsy. Fifteen (65%) had Grade Group 1 disease, and all others had Grade Group 2 disease. Seven (30%) had favorable- to intermediate-risk disease. Of 22 evaluable patients, 13 (59%) had no residual cancer on post-treatment biopsy. The median time to first positive biopsy was 364 days (95% CI: 91-742 days). The impact of apalutamide on quality of life was minimal and transient. Decipher risk classifier revealed a greater number of negative post-treatment biopsies in those with higher baseline genomic risk score (P = .01).

CONCLUSIONS

The negative repeat biopsy rate following 90 days of apalutamide was high in men with prostate cancer followed on active surveillance. Apalutamide was safe, well tolerated, and had minimal impact on quality of life. Randomized studies evaluating the effects of apalutamide in men enrolled on active surveillance are warranted.

Transcriptomic discriminators of response to apalutamide in patients with prostate cancer (PC) on active surveillance (AS)

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Background: We previously reported the results of a Phase 2 study showing that a high proportion (59%) of men with PC being followed on AS will have a negative post-treatment biopsy after 90 days of apalutamide (Schweizer, et al. SUO Annual Meeting 2020). In order to identify candidate biomarkers for response, we conducted transcriptional profiling of tumor tissue obtained from men enrolled to the aforementioned trial. Methods: We analyzed FFPE tissue obtained from men enrolled to a Phase II study testing 90-days of apalutamide. Transcript profiles were assessed using Affymetrix Microarrays (Decipher Biosciences, Inc). Differences in signaling pathways were assessed between samples at baseline, day (D) 91 (post-treatment) and at D365. We also assessed differences in signaling pathways between patients that did vs. did not have a response (i.e. negative vs. persistent cancer on surveillance biopsy) at D91, which was the primary endpoint of the study. All comparisons were made using a Wilcoxon signed rank test unless otherwise indicated. Results: Samples from 22 subjects who completed 3-months of apalutamide and subsequently underwent post-treatment biopsy were available for analysis. From 19 Baseline and 15 post-treatment tissue samples, 25 passed pathology quality control (N = 12 at baseline, N = 8 at D91 and N = 5 at D365). Principal component analysis revealed distinct transcriptional profiles between tumor samples analyzed at baseline vs. D91. Surprisingly, D365 specimens still demonstrated a distinct profile compared to both baseline and D91 samples. Pathway analysis revealed up-regulation of angiogenesis signaling at D91 (P < 0.01) and D365 (P = 0.03) compared to baseline. As expected, estrogen (P < 0.01) and androgen receptor (P = 0.02) signaling were significantly lower at D91; however, only estrogen signaling was persistently suppressed at D365 (P = 0.03). Basal pathway signatures and markers associated with inflammatory response were also significantly upregulated at D91. There were no significant differences in Gleason grade group (GG) between responders and non-responders: 8/15 (53%) with GG1 vs. 5/7 (71%) with GG2 (Fisher’s exact P = 0.648). Decipher (P = 0.01) and Cuzick (P = 0.03) risk classifiers revealed an enrichment for responses in those with higher risk disease at baseline. There was also an enrichment for responses in those with higher nucleotide excision repair signature (P = 0.03) and those with signatures associated with TP53 mutations (P = 0.02). Conclusions: We observed significant transcriptional changes following 90 days of apalutamide, with evidence of persistent differences up to one year after enrollment. Higher baseline risk score was associated with improved responses to apalutamide treatment. Prospective studies evaluating the benefit of apalutamide in men on AS with higher risk transcriptional profiles are warranted. Clinical trial information: NCT02721979.

Targeting backdoor androgen synthesis through AKR1C3 inhibition: A presurgical hormonal ablative neoadjuvant trial in high-risk localized prostate cancer

BACKGROUND

Localized prostate cancers (PCs) may resist neoadjuvant androgen receptor (AR)-targeted therapies as a result of persistent intraprostatic androgens arising through upregulation of steroidogenic enzymes. Therefore, we sought to evaluate clinical effects of neoadjuvant indomethacin (Indo), which inhibits the steroidogenic enzyme AKR1C3, in addition to combinatorial anti-androgen blockade, in men with high-risk PC undergoing radical prostatectomy (RP).

METHODS

This was an open label, single-site, Phase II neoadjuvant trial in men with high to very-high-risk PC, as defined by NCCN criteria. Patients received 12 weeks of apalutamide (Apa), abiraterone acetate plus prednisone (AAP), degarelix, and Indo followed by RP. Primary objective was to determine the pathologic complete response (pCR) rate. Secondary objectives included minimal residual disease (MRD) rate, defined as residual cancer burden (RCB) ≤ 0.25cm³ (tumor volume multiplied by tumor cellularity) and elucidation of molecular features of resistance.

RESULTS

Twenty patients were evaluable for the primary endpoint. Baseline median prostate-specific antigen (PSA) was 10.1 ng/ml, 4 (20%) patients had Gleason grade group (GG) 4 disease and 16 had GG 5 disease. At RP, 1 (5%) patient had pCR and 6 (30%) had MRD. Therapy was well tolerated. Over a median follow-up of 23.8 months, 1 of 7 (14%) men with pathologic response and 6 of 13 (46%) men without pathologic response had a PSA relapse. There was no association between prostate hormone levels or HSD3B1 genotype with pathologic response.

CONCLUSIONS

In men with high-risk PC, pCR rates remained low even with combinatorial AR-directed therapy, although rates of MRD were higher. Ongoing follow-up is needed to validate clinical outcomes of men who achieve MRD.

Targeting backdoor androgen synthesis through AKR1C3 inhibition: A presurgical hormonal ablative trial in high risk localized prostate cancer (PC)

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Background: Studies have shown that localized PCs may resist neoadjuvant androgen receptor (AR)-targeted therapies as a result of persistent intraprostatic androgens, likely arising through upregulation of steroidogenic enzymes. Therefore, we sought to evaluate clinical effects of combinatorial AR-targeted therapy, including indomethacin (Indo) to inhibit the steroidogenic enzyme AKR1C3, in men with high risk PC undergoing radical prostatectomy (RP). Methods: This was an open label, single-site, Phase II neoadjuvant trial in men with localized high to very-high risk PC, as defined by NCCN criteria. Patients received 12 weeks of neoadjuvant apalutamide (Apa), abiraterone (Abi) plus prednisone, degarelix, and Indo at their respective FDA-approved doses followed by RP. The primary objective was to determine the pathologic complete response (pCR) rate. Secondary objectives included assessing for minimal residual disease (MRD) (i.e. ≤0.25 cm3 tumor volume corrected for cellularity), measuring intraprostatic androgens and assessing molecular features associated with drug resistance. Twenty evaluable patients provided 91% power (one-sided alpha = 7.5%) to detect a difference in pCR rate of 5% (H0) vs. 25% (H1). Results: Twenty-two patients enrolled and 20 were evaluable for the primary endpoint (1 patient came off to pursue stereotactic radiosurgery; 1 was removed after developing grade 2 transaminitis). At baseline, the median PSA was 10.1 ng/mL (4.4-159.4), 4 (20%) patients had Gleason grade group (GG) 4 disease and 16 had GG 5 disease. At RP, 1 (5%) patient had a pCR, 6 (30%) had MRD, 18 (90%) had ypT3 disease and 7 (35%) had lymph node (LN) metastases. Treatment was generally well tolerated and adverse events were consistent with each individual drug’s known safety profile. Additional follow up data and correlative work will be presented at the meeting. Conclusions: In our cohort of men with high-risk PC, pCR rates remained low even with combinatorial AR-directed therapy. Ongoing pharmacodynamic studies aimed at determining if Indo effectively inhibited AKR1C3 will provide important insights regarding the utility of targeting this steroidogenic enzyme. Clinical trial information: NCT02849990.