Phase Ib Dose Expansion and Translational Analyses of Olaparib in Combination with Capivasertib in Recurrent Endometrial, Triple-Negative Breast, and Ovarian Cancer

Abstract

Purpose: On the basis of strong preclinical rationale, we sought to confirm recommended phase II dose (RP2D) for olaparib, a PARP inhibitor, combined with the AKT inhibitor capivasertib and assess molecular markers of response and resistance.

Patients and methods: We performed a safety lead-in followed by expansion in endometrial, triple-negative breast, ovarian, fallopian tube, or peritoneal cancer. Olaparib 300 mg orally twice daily and capivasertib orally twice daily on a 4-day on 3-day off schedule was evaluated. Two dose levels (DL) of capivasertib were planned: 400 mg (DL1) and 320 mg (DL-1). Patients underwent biopsies at baseline and 28 days.

Results: A total of 38 patients were enrolled. Seven (18%) had germline BRCA1/2 mutations. The first 2 patients on DL1 experienced dose-limiting toxicities (DLT) of diarrhea and vomiting. No DLTs were observed on DL-1 (n = 6); therefore, DL1 was reexplored (n = 6) with no DLTs, confirming DL1 as RP2D. Most common treatment-related grade 3/4 adverse events were anemia (23.7%) and leukopenia (10.5%). Of 32 evaluable subjects, 6 (19%) had partial response (PR); PR rate was 44.4% in endometrial cancer. Seven (22%) additional patients had stable disease greater than 4 months. Tumor analysis demonstrated strong correlations between response and immune activity, cell-cycle alterations, and DNA damage response. Therapy resistance was associated with receptor tyrosine kinase and RAS-MAPK pathway activity, metabolism, and epigenetics.

Conclusions: The combination of olaparib and capivasertib is associated to no serious adverse events and demonstrates durable activity in ovarian, endometrial, and breast cancers, with promising responses in endometrial cancer. Importantly, tumor samples acquired pre- and on-therapy can help predict patient benefit.

Figure 1.. Clinical outcomes.

(A) Waterfall plot of best response to olaparib and capivasertib among evaluable patients (n=32); (B) Swimmer plot of duration on study for all evaluable patients (n=32). (C) Longitudinal nausea and fatigue during first 8 weeks of therapy, fatigue between responders and non-responders, interference with physical functioning (walking, activity, work) between responders and non-repsonders.

Figure 2:. Molecular mechanisms driving the response to therapy. DNA alterations.

(A) Cohort Distribution for DNA alterations by Response Category. Mutations were aggregated from CLIA-panel and WES, insertion and deletions were called from WES. Alterations were aggregated across PRE and ON-treatment samples for each patient. (B) Pathway Enrichment for DNA Alterations, by Response Group. For each response group (PR, SD, and PD), pathways that had an over-representation of altered genes (using both mutation and insertion/deletions) were assessed. Pathway categories are shown on the plot according to number of genes hit in the pathway as well as number of patients with gene alterations, colored according to response group. FDR shown on plot is the minimum of the set of pathways that were collapsed. Full pathway table of top enriched pathways can be found in Supplementary Table S2. Gene expression. (C) Heatmap representing the hierarchical unsupervised clustering of the RNA expression in pre- and on-treatment sample of all patient. Only the most significant genes between PR and PD patients were included. (D) GSEA was performed to compare the expression of genes between PR and PD patients. The most representative pathways enriched in either PR and PD patient’s samples were included. Protein expression. (E) RPPA analysis was used to determine protein alteration in the on-treatment samples compared to pre-treatment. Level of total PARylation and phosphorylated GSK3a-b (S21/S9) was measured in the different outcome groups. A paired t-test was used to assess the significant differences between the different groups. P ≤ 0.05 is considered significant. (F) Heatmap representing the hierarchical unsupervised clustering of the on to pre-treatment ratio of all proteins and patient samples. Most relevant proteins involved in the cell cycle and DNA damage response, signaling pathways, immune system and epigenetics are identified.(G) Pathway analysis comparing pre, on and on to pre change in all samples. The heat maps were constructed using hierarchical unsupervised clustering of both the pathway scores and the samples. A full list of predictors used to calculate the pathways can be found in Supplementary Table S3. Kaplan-Meyer curves were built using the days on treatment for patients with high and low (H) RTK and RAS-MAPK pathway activity pre-treatment, (I) replication stress and DNA damage response on-therapy and (J) immune/INF gene expression on-therapy. Patients with RAS mutation were included in the high RTK-RAS-MAPK group. Only patients with RNA sequencing data were included in the immune/INF Kaplan-Meyer curve. (K) Kaplan-Meyer curves showing PI3K-AKT-mTOR inhibition status with and without DNA damage response (DDR). Each patient group was defined based on the pathway scores showed in Figure 2G.

Figure 3.. PDX model.

A TNBC PDX model was implanted in NGS mice and treated with a vehicle, olaparib, capivasertib or their combination. (A) tumor growth was assessed and (B) protein were analyzed by RPPA. The heat map representing the hierarchical unsupervised clustering of all proteins with different level of expression across treatment groups. Groups of proteins that were altered by AKT only (green), AKT and the combination (blue), PARP and the combination (purple) and the combination alone (red) were identified. A student t.test was used to compare the tumor growth between control mice and mice treated with olaparib, capivasertib or their combination. **:p<0.01, ***p<0.001. § indicates a significant difference between the tumor size of capivasertib treated mice and mice treated with the combination.