Olaparib in patients with mCRPC with homologous recombination repair gene alterations: PROfound Asian subset analysis.

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.

DNA damage-induced cellular senescence is sufficient to suppress tumorigenesis: a mouse model.

Tumor suppressor p53-dependent apoptosis is critical in suppressing tumorigenesis. Previously, we reported that DNA double-strand breaks (DSBs) at the V(D)J recombination loci induced genomic instability in the developing lymphocytes of nonhomologous end-joining (NHEJ)-deficient, p53-deficient mice, which led to rapid lymphomagenesis. To test the ability of p53-dependent cell cycle arrest to suppress tumorigenesis in the absence of apoptosis in vivo, we crossbred NHEJ-deficient mice into a mutant p53R172P background; these mice have defects in apoptosis induction, but not cell cycle arrest. These double-mutant mice survived longer than NHEJ/p53 double-null mice and, remarkably, were completely tumor free. We detected accumulation of aberrant V(D)J recombination-related DSBs at the T cell receptor (TCR) locus, and high expression levels of both mutant p53 and cell cycle checkpoint protein p21, but not the apoptotic protein p53-upregulated modulator of apoptosis. In addition, a substantial number of senescent cells were observed among both thymocytes and bone marrow cells. Cytogenetic studies revealed euploidy and limited chromosomal breaks in these lymphoid cells. The results indicate that precursor lymphocytes, which normally possess a high proliferation potential, are able to withdraw from the cell cycle and undergo senescence in response to the persistence of DSBs in a p53-p21-dependent pathway; this is sufficient to inhibit oncogenic chromosomal abnormality and suppress tumorigenesis.

Olaparib plus Abiraterone for Metastatic Castration-resistant Prostate Cancer: Pharmacokinetics Data from the PROpel Trial.

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 Δ4-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. Δ4-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.

Efficacy and Determinants of Response to HER Kinase Inhibition in HER2-Mutant Metastatic Breast Cancer.

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.

Impact of FDG PET Imaging for Expanding Patient Eligibility and Measuring Treatment Response in a Genome-Driven Basket Trial of the Pan-HER Kinase Inhibitor, Neratinib.

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.

Mutations within the kinase domain and truncations of the epidermal growth factor receptor are rare events in bladder cancer: implications for therapy.

PURPOSE: It has previously been reported that the patient response to gefitinib depends on the presence of mutations within the kinase domain of epidermal growth factor receptor (EGFR) or the expression of its truncated form, EGFR variant III (EGFRvIII). The focus of this study was to determine if these alterations are present within the tyrosine kinase and ligand-binding domain of EGFR in urothelial carcinoma. EXPERIMENTAL DESIGN: The kinase domain found within exons 18 to 21 of the EGFR from 11 bladder cancer cell lines and 75 patient tumors were subjected to automated sequencing. EGFRvIII expression was determined by immunohistochemistry using a urothelial carcinoma tissue microarray, and its expression was subsequently verified by reverse transcription PCR, real-time PCR, and Western blot analysis, using an EGFRvIII-transfected glioblastoma cell line and glioblastoma tumors as positive controls. RESULTS: Our analysis failed to detect mutations within the tyrosine kinase domain of EGFR in the 11 cell lines and 75 patients tested. The initial analysis of EGFRvIII expression by immunohistochemistry revealed that at least 50% of the patient tumors expressed EGFRvIII in a urothelial carcinoma tissue microarray. Conflicting reports exist, however, regarding the extent of EGFRvIII expression in tissues owing to the specificity of the antibodies and the methodologies used. Therefore, we sought to validate this observation by reverse transcription PCR, real-time PCR, and Western blot analysis. In these assays, none of the samples were positive for EGFRvIII except for control transfectants and glioblastomas. CONCLUSIONS: When our results are taken together, we conclude that alterations within the tyrosine kinase domain and expression of EGFRvIII are rare events in bladder cancer. The present study has clinical implications in selecting tyrosine kinase inhibitors for the therapy of urothelial carcinoma.

NPI-0052, a novel proteasome inhibitor, induces caspase-8 and ROS-dependent apoptosis alone and in combination with HDAC inhibitors in leukemia cells.

The proteasome has been successfully targeted for the treatment of multiple myeloma and mantle cell lymphoma; however, in other hematologic malignancies, bortezomib has been less effective as a single agent. Here, we describe effects of NPI-0052, a novel proteasome inhibitor, in leukemia model systems. In cell lines, NPI-0052 inhibits all 3 proteolytic activities associated with the proteasome: chymotrypsin-, trypsin-, and caspase-like. NPI-0052 also induces DNA fragmentation in leukemia lines and in mononuclear cells from a Ph + acute lymphoblastic leukemia (ALL) patient. Caspase-3 activation by NPI-0052 was seen in wild-type Jurkat cells, but was significantly lessened in Fas-associated death domain (FADD)-deficient or caspase-8-deficient counterparts. NPI-0052-induced apoptosis was further probed using caspase-8 inhibitors, which were more protective than caspase-9 inhibitors. N-acetyl cysteine (NAC) also conferred protection against NPI-0052-induced apoptosis, indicating a role for oxidative stress by NPI-0052. In support of the drug's in vitro activities, biweekly treatment with NPI-0052 lessened total white blood cell (WBC) burden over 35 days in leukemic mice. Interestingly, combining NPI-0052 with either MS-275 or valproic acid (VPA) induced greater levels of cell death than the combination of bortezomib with these histone deacetylase inhibitors (HDACi). These effects of NPI-0052, alone and in combination with HDACi, warrant further testing to determine the compound's clinical efficacy in leukemia.