Andrew Armstrong

<jats:p> 39 </jats:p><jats:p> Background: The presence of progressing cancer, male sex and advanced age have been shown to increase the severity of coronavirus disease 2019 (COVID-19). Given that the androgen regulated gene TMPRSS2 has been implicated in SARS-CoV-2 viral entry, we hypothesized that ADT may improve COVID-19 outcomes. This analysis evaluated clinical outcomes of pts with PCa with concurrent SARS-CoV-2 infection and investigated the impact of ADT on occurrence of severe-COVID-19 and mortality. Methods: Data was obtained via the COVID-19 and Cancer Consortium (CCC19), a multicenter registry including &gt;120 cancer centers with de-identified data from pts with COVID-19 and cancer. Men with confirmed SARS-CoV-2 infection and a primary diagnosis of prostate cancer were included: data cutoff of July 31, 2020. The primary endpoint was the development of severe-COVID-19 (death, ICU admission, or mechanical ventilation) among pts on ADT vs. those not on ADT at time of COVID-19 infection. Secondary endpoints included 30-day mortality based on ADT use. Mortality and development of severe-COVID-19 were assessed in Pts grouped by therapy: 1st generation androgen receptor inhibitor (ARI-1), 2nd generation ARI (darolutamide, enzalutamide, apalutamide, ARI-2), abiraterone/prednisone, and chemotherapy. Propensity score matching was utilized. Logistic regression was utilized to adjust for age, ECOG PS, comorbidities, and race. Results: 589 pts were included; median follow-up was 42 days (IQR 25-90) and 62% (363/589) were hospitalized. Severe-COVID-19 developed in 28% of pts and the all-cause 30-day mortality rate was 19%. There was no significant difference in the development of severe-COVID-19 or 30-day mortality between Pts on ADT vs not on ADT, whether using descriptive statistics with the entire population or using the propensity score matched population (Table). Among the descriptive population, the numerical rates of severe-COVID-19 and mortality were lowest in Pts receiving ARI-2, but sample size was low. Conclusions: The overall 30-day mortality rate and percentage developing severe-COVID-19 were high. There was no statistical difference in the development of severe-COVID-19 or mortality based on receipt of ADT; however, this analysis is limited by the retrospective nature and small N after propensity-matching. [Table: see text] </jats:p>

<jats:p> 12 </jats:p><jats:p> Background: CheckMate 9KD (NCT03338790) is a phase 2 trial of nivolumab (NIVO; anti-PD-1) in combination with rucaparib, docetaxel (DOCE), or enzalutamide for patients with metastatic castration-resistant prostate cancer (mCRPC). DOCE is a standard-of-care chemotherapy for mCRPC that may potentiate antitumor immune responses, thus supporting its use in combination with NIVO, which has shown limited antitumor activity in mCRPC as monotherapy. We report final analysis results for Arm B (NIVO + DOCE) of CheckMate 9KD. Methods: Arm B enrolled patients with chemotherapy-naive mCRPC with ongoing androgen deprivation therapy and ≤ 2 prior novel antiandrogen therapies (NATs; i.e., abiraterone, enzalutamide, etc.). Patients received NIVO 360 mg + DOCE 75 mg/m<jats:sup>2</jats:sup> Q3W + prednisone 5 mg BID for ≤ 10 cycles, followed by NIVO 480 mg Q4W until disease progression/unacceptable toxicity (up to 2 years). Coprimary endpoints were objective response rate (ORR) and prostate-specific antigen response rate (PSA-RR; defined as a ≥ 50% PSA reduction). Secondary endpoints included radiographic progression-free survival (rPFS), overall survival (OS), and safety. Results: Of 84 treated patients with a median age of 71 years (range: 53-88), 27% had visceral disease and 54% had measurable disease. The median number of docetaxel cycles was 8; the median number of nivolumab doses was 11. Median follow up was 15.2 months. The table displays the efficacy outcomes, which appear to show comparable ORR in patients receiving versus not receiving prior NAT. There was 1 (2.2%) complete objective response and 17 (37.8%) partial responses in 45 patients with measurable disease. Any-grade treatment-related AEs (TRAEs) occurred in 95.2% of patients, most commonly fatigue (39.3%), diarrhea (35.7%), and alopecia (34.5%). Grade 3-4 TRAEs occurred in 47.6% of patients, most commonly neutropenia (16.7%). TRAEs led to discontinuation in 29.8% of patients. The most common immune-related AEs were GI (35.7%) or skin-related (26.2%). There were 3 treatment-related deaths (1 pneumonitis related to NIVO; 2 pneumonias related to DOCE). Conclusions: NIVO + DOCE has encouraging clinical activity in patients with chemotherapy-naïve mCRPC, regardless of prior NAT, with a safety profile consistent with those of the individual agents. These outcomes support the ongoing phase 3 CheckMate 7DX trial of NIVO + DOCE vs placebo + DOCE for mCRPC (NCT04100018). Clinical trial information: NCT03338790. [Table: see text] </jats:p>

PURPOSE: To evaluate the prognostic significance of circulating tumour cell (CTC) number determined on the Epic Sciences platform in men with metastatic castration-resistant prostate cancer (mCRPC) treated with an androgen receptor signalling inhibitor (ARSI). PATIENTS AND METHODS: A pre-treatment blood sample was collected from men with progressing mCRPC starting either abiraterone or enzalutamide as a first-, second- or third-line systemic therapy at Memorial Sloan Kettering Cancer Center (Discovery cohort, N = 171) or as a first- or second-line therapy as part of the multicenter PROPHECY trial (NCT02269982) (Validation cohort, N = 107). The measured CTC number was then associated with overall survival (OS) in the Discovery cohort, and progression-free survival (PFS) and OS in the Validation cohort. CTC enumeration was also performed on a concurrently obtained blood sample using the CellSearch® Circulating Tumor Cell Kit. RESULTS: In the MSKCC Discovery cohort, CTC count was a statistically significant prognostic factor of OS as a dichotomous (<3 CTCs/mL versus ≥ 3 CTCs/mL; hazard ratio [HR] = 1.8 [95% confidence interval {CI} 1.3-3.0]) and a continuous variable when adjusting for line of therapy, presence of visceral metastases, prostate-specific antigen, lactate dehydrogenase and alkaline phosphatase. The findings were validated in an independent datas et from PROPHECY (HR [95% CI] = 1.8 [1.1-3.0] for OS and 1.7 [1.1-2.9] for PFS). A strong correlation was also observed between CTC counts determined in matched samples on the CellSearch® and Epic platforms (r = 0.84). CONCLUSION: The findings validate the prognostic significance of pretreatment CTC number determined on the Epic Sciences platform for predicting OS in men with progressing mCRPC starting an ARSI.

<jats:p> TPS183 </jats:p><jats:p> Background: Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a cell surface antigen that is highly expressed in prostate cancer. AMG 509 is a potent bispecific XmAb 2+1 immune therapy designed to direct T effector cells to STEAP1-expressing cells. AMG 509 contains two identical humanized anti-STEAP1 Fab domains that bind STEAP1-expressing cells, an anti-CD3 scFv domain that binds T cells, and an Fc domain, engineered to lack effector function, that extends serum half-life. In preclinical studies, AMG 509 induced potent and specific T-cell-mediated lysis of STEAP1-expressing cancer models. Methods: This open-label, phase 1, first-in-human study will evaluate the safety, tolerability, pharmacokinetics (PK), and efficacy of AMG 509 in patients with relapsed/refractory mCRPC. The dose exploration phase (n=40) will estimate the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) using a Bayesian logistic regression model. The dose expansion phase (n=30) will confirm safety, PK, and pharmacodynamics at the MTD or RP2D and collect further safety, efficacy, and biomarker data. Efficacy will be assessed by prostate-specific antigen response, circulating tumor cell response, and objective tumor response per RECIST 1.1 with Prostate Cancer Working Group 3 modifications. Key inclusion criteria: men ≥18 years with histologically/cytologically confirmed mCRPC who are refractory to novel hormonal therapy (e.g., abiraterone and/or enzalutamide) and have failed 1–2 taxane regimens or are medically unsuitable for or have refused taxanes; ongoing castration with total serum testosterone ≤50 ng/dL; evidence of progressive disease; ECOG performance status 0–1; life expectancy ≥3 months; and adequate hematologic, renal, hepatic, and cardiac function. In the dose exploration phase, novel antiandrogen therapy must have been given in the metastatic setting. Key exclusion criteria: pure small cell or neuroendocrine carcinoma of the prostate; untreated CNS metastases or leptomeningeal disease; any anticancer therapy or immunotherapy, radiation therapy, or major surgery &lt;4 weeks from first dose; history of or current autoimmune disease or any disease requiring immunosuppressive therapy (≤10 mg/d prednisone permitted); prior STEAP1-targeted therapy; infection requiring IV antimicrobials &lt;7 days from first dose. The study opened in January 2020 and is recruiting patients. ClinicalTrials.gov: NCT04221542. 2020 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2020 ASCO Annual Meeting. All rights reserved. Clinical trial information: NCT04221542. </jats:p>

<jats:p> 90 </jats:p><jats:p> Background: ADT with salvage RT improves survival for men with PSA recurrence after RP. Current standard duration of ADT for high risk PSA recurrence is up to 2 years with RT; therefore shortening but intensifying systemic therapy may improve outcomes. The STREAM trial showed 6 mo of enzalutamide added to ADT/RT had a 3-year progression free survival (PFS) of 53% in high risk patients including lymph node (LN) positive. Given that docetaxel improves survival in men with mHSPC, we evaluated the combination of salvage RT, ADT/apalutamide and docetaxel in this setting. Methods: STARTAR is a multicenter phase 2 trial for salvage treatment of PSA recurrent PC following RP conducted within the US Dept. of Defense Prostate Cancer Clinical Trials Consortium (DOD PCCTC). Key inclusion criteria included PC with Gleason 7 with T3/positive margin/1-4 positive LNs or Gleason 8-10 disease and PSA relapse within 4 years of RP (min PSA 0.2 ng/mL to max PSA 4 ng/mL). Men with up to 4 positive resected LNs were eligible. Men started ADT with apalutamide, continued with RT (66-74 Gy to the prostate bed +/- pelvic LNs over 6-8 weeks), and finally completed docetaxel 75mg/m2 IV q3 weeks for 6 cycles. Men were treated with ADT and apalutamide for approximately 9 months. The primary endpoint was PSA PFS at 36 months. This interim analysis evaluated secondary endpoints of 1-year PSA recurrence, testosterone recovery, and safety of this treatment sequence. Results: From 3/2018 to 12/2019, 39 men were enrolled at Duke, Wake Forest, Cornell, and the GU Research Network. With a data cutoff in 9/2020, median follow up from enrollment was 14 months. Baseline patient characteristics included Gleason 4+3 = 7 in 54% and Gleason 8-10 in 46%, and 23% LN positive; median PSA at the time of enrollment was 0.58 ng/mL (range 0.21-3.40) and the median time from RP to enrollment was 7 mo (range 2-98). At 1 year, there have been no progression events with 38% (12/31) of men with post-treatment testosterone recovery into normal range (recovery time median 10 mos [1-17 mos]). Common adverse events (AEs) of any-grade at least possibly related to the regimen were 98% hot flashes, 88% fatigue, 77% alopecia, 57% dysgeusia, and 53% rash (28% grade 1; 15% grade 2, 10% grade 3), with neutropenia as the most common grade 3/4 AE (27/39 men, 70%) with two grade 3 febrile neutropenia. Conclusions: In this first phase 2 trial of ADT, apalutamide, radiation, and 6 cycles docetaxel in the salvage setting for high risk PSA recurrence, short term outcomes are excellent with no recurrences at 12 months of follow-up. This salvage treatment was well tolerated in the majority of men with the exception of a high rate of drug rashes and neutropenia related to the course of treatment, in line with known safety profiles of the study agents. Clinical trial information: NCT03311555. </jats:p>