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PROpel (NCT03732820) was a positive phase 3 trial that demonstrated a clinically significant improvement in radiographic progression-free survival with olaparib plus abiraterone versus placebo plus abiraterone in first-line metastatic castration-resistant prostate cancer. For a subset of PROpel patients, steady-state concentrations of olaparib, abiraterone, and Δ 4 -abiraterone were measured in blood samples collected before and at several time points after dose administration. The pharmacokinetics (PK) for each drug and metabolite were evaluated to determine whether any clinically relevant drug-drug interactions between olaparib and abiraterone occurred. The results demonstrate that steady-state PK parameters for olaparib and abiraterone in PROpel were comparable with those in monotherapy trials. Abiraterone steady-state exposures were similar between treatment arms. Δ 4 -Abiraterone had slightly lower steady-state exposures when abiraterone was administered in combination with olaparib. These results are consistent with a previous phase 2 study, supporting the conclusion that no clinically relevant PK-based drug-drug interactions occurred when olaparib and abiraterone were given in combination at their full monotherapy doses. PATIENT SUMMARY: When drugs are administered in combination, a key consideration is whether there are any interactions between the drugs that may affect their activity. We analyzed blood concentrations of olaparib and abiraterone in a subset of patients with prostate cancer from the PROpel trial to determine if there were interactions between these two drugs. We found that there was no significant effect on the profile of either drug when they were given together at the same doses used when each drug is given individually., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: The Phase III PROfound study (NCT02987543) evaluated olaparib versus abiraterone or enzalutamide (control; randomized 2:1 to olaparib or control) in men with homologous recombination repair gene alterations and metastatic castration-resistant prostate cancer whose disease progressed on prior next-generation hormonal agent., Methods: We present efficacy and safety data from an exploratory post hoc analysis of olaparib in the PROfound Asian subset. Analyses were not planned, alpha controlled or powered. Of 101 Asian patients enrolled in Japan (n=57), South Korea (n=29) and Taiwan (n=15), 66 and 35 patients received olaparib and control, respectively., Results: Radiographic progression-free survival (rPFS) and overall survival (OS) favored olaparib versus control in Cohort A [rPFS 7.2 vs. 4.5 months, HR 0.58, 95% CI 0.29-1.21, P = 0.14 (nominal); OS 23.4 vs. 17.8 months, HR 0.81, 95% CI 0.40-1.74, P = 0.57 (nominal)] and Cohorts A+B [rPFS 5.8 vs. 3.5 months, HR 0.69, 95% CI 0.42-1.16, P = 0.13 (nominal); OS 18.6 vs. 16.2 months, HR 0.96, 95% CI 0.56-1.70, P = 0.9 (nominal)]. Olaparib showed greatest improvement in patients harboring BRCA alterations [rPFS 9.3 vs. 3.5 months, HR 0.17, 95% CI 0.06-0.49, P = 0.0003 (nominal); OS 26.8 vs. 14.3 months, HR 0.62, 95% CI 0.24-1.79, P = 0.34 (nominal)]. Safety data were consistent with the known profile of olaparib, with no new safety signals identified., Conclusion: In PROfound, there was a statistically significant improvement in outcomes reported in the global population of patients with metastatic castration-resistant prostate cancer and alterations in homologous recombination repair genes whose disease progressed on prior next-generation hormonal agent compared with control. For the subset of Asian patients reported here, exploratory analysis suggested that there was also an improvement in outcomes versus control. The safety and tolerability of olaparib in Asian patients were similar to that of the PROfound global population., Clinical Trial Number: ClinicalTrials.gov NCT02987543., (© The Author(s) 2022. Published by Oxford University Press.)

HER2 mutations define a subset of metastatic breast cancers with a unique mechanism of oncogenic addiction to HER2 signaling. We explored activity of the irreversible pan-HER kinase inhibitor neratinib, alone or with fulvestrant, in 81 patients with HER2 -mutant metastatic breast cancer. Overall response rate was similar with or without estrogen receptor (ER) blockade. By comparison, progression-free survival and duration of response appeared longer in ER + patients receiving combination therapy, although the study was not designed for direct comparison. Preexistent concurrent activating HER2 or HER3 alterations were associated with poor treatment outcome. Similarly, acquisition of multiple HER2 -activating events, as well as gatekeeper alterations, were observed at disease progression in a high proportion of patients deriving clinical benefit from neratinib. Collectively, these data define HER2 mutations as a therapeutic target in breast cancer and suggest that coexistence of additional HER signaling alterations may promote both de novo and acquired resistance to neratinib. SIGNIFICANCE: HER2 mutations define a targetable breast cancer subset, although sensitivity to irreversible HER kinase inhibition appears to be modified by the presence of concurrent activating genomic events in the pathway. These findings have implications for potential future combinatorial approaches and broader therapeutic development for this genomically defined subset of breast cancer. This article is highlighted in the In This Issue feature, p. 161 ., (©2019 American Association for Cancer Research.)

Purpose: To determine whether FDG PET can expand eligibility in biomarker-selected clinical trials by providing a means to quantitate response in patients with non-assessable disease by RECIST., Experimental Design: SUMMIT (NCT01953926) is a multicenter phase II "basket" trial of the Pan-HER kinase inhibitor, neratinib. Patients had advanced ERBB2 (HER2)-mutant solid tumors, ≥1 measurable lesion, preferably defined unidimensionally by RECIST v1.1, or alternatively metabolically by PET Response Criteria (PRC). The primary aim was to determine the proportion of additional breast cancer patients accrued using PRC who would have otherwise been ineligible based on RECIST criteria alone. The secondary aim was to determine the concordance of response versus non-response between RECIST and PRC., Results: Eighty-one patients with HER2-mutant metastatic breast cancer were accrued; 77 were evaluable for response by RECIST and/or PRC. 63 (82%) were RECIST-evaluable and 14 (18%) were accrued using PRC alone. Bone-only disease ( n = 11; 79%) was the most common reason for classification as non-measurable by RECIST. Twenty-nine patients were accrued and followed using both criteria, of which 25 (86%; 95% confidence interval, 68%-96%) were concordant for response versus non-response as defined by RECIST and PRC., Conclusions: PRC allowed patients with non-RECIST measurable disease access to therapy and facilitated more rapid accrual of patients to this trial of a rare biomarker. PRC and RECIST both provided methods of response assessment and were generally concordant. Thus, PRC was useful as a supplement to RECIST criteria. This provides a rationale for including FDG PET measurements in future clinical trials involving rare tumors or rare genomically defined subpopulations of more common cancers., (©2019 American Association for Cancer Research.)