Selective AKT kinase inhibitor capivasertib in combination with fulvestrant in PTEN-mutant ER-positive metastatic breast cancer.

Five to ten percent of ER+ metastatic breast cancer (MBC) tumors harbor somatic PTEN mutations. Loss of function of this tumor-suppressor gene defines a highly aggressive, treatment-refractory disease for which new therapies are urgently needed. This Phase I multipart expansion study assessed oral capivasertib with fulvestrant in patients with PTEN-mutant ER+ MBC. Safety and tolerability were assessed by standard methods. Plasma and tumor were collected for NGS and immunohistochemistry analyses of PTEN protein expression. In 31 eligible patients (12 fulvestrant naive; 19 fulvestrant pretreated), the 24-week clinical benefit rate was 17% in fulvestrant-naive and 42% in fulvestrant-pretreated patients, with objective response rate of 8% and 21%, respectively. Non-functional PTEN was centrally confirmed in all cases by NGS or immunohistochemistry. Co-mutations occurred in PIK3CA (32%), with less ESR1 (10% vs 72%) and more TP53 (40% vs 28%) alterations in fulvestrant-naive versus fulvestrant-pretreated patients, respectively. PTEN was clonally dominant in most patients. Treatment-related grade ≥3 adverse events occurred in 32% of patients, most frequently diarrhea and maculopapular rash (both n = 2). In this clinical study, which selectively targeted the aggressive PTEN-mutant ER+ MBC, capivasertib plus fulvestrant was tolerable and clinically active. Phenotypic and genomic differences were apparent between fulvestrant-naive and -pretreated patients.Trial registration number for the study is NCT01226316.

Capivasertib, an AKT Kinase Inhibitor, as Monotherapy or in Combination with Fulvestrant in Patients with AKT1 E17K-Mutant, ER-Positive Metastatic Breast Cancer.

PURPOSE: The activating mutation AKT1 E17K occurs in approximately 7% of estrogen receptor-positive (ER+) metastatic breast cancer (MBC). We report, from a multipart, first-in-human, phase I study (NCT01226316), tolerability and activity of capivasertib, an oral AKT inhibitor, as monotherapy or combined with fulvestrant in expansion cohorts of patients with AKT1 E17K-mutant ER+ MBC. PATIENTS AND METHODS: Patients with an AKT1 E17K mutation, detected by local (next-generation sequencing) or central (plasma-based BEAMing) testing, received capivasertib 480 mg twice daily, 4 days on, 3 days off, weekly or 400 mg twice daily combined with fulvestrant at the labeled dose. Study endpoints included safety, objective response rate (ORR; RECIST v1.1), progression-free survival (PFS), and clinical benefit rate at 24 weeks (CBR24). Biomarker analyses were conducted in the combination cohort. RESULTS: From October 2013 to August 2018, 63 heavily pretreated patients received capivasertib (20 monotherapy, 43 combination). ORR was 20% with monotherapy, and within the combination cohort was 36% in fulvestrant-pretreated and 20% in fulvestrant-naïve patients, although the latter group may have had more aggressive disease at baseline. AKT1 E17K mutations were detectable in plasma by BEAMing (95%, 41/43), droplet digital PCR (80%, 33/41), and next-generation sequencing (76%, 31/41). A ≥50% decrease in AKT1 E17K at cycle 2 day 1 was associated with improved PFS. Combination therapy appeared more tolerable than monotherapy [most frequent grade ≥3 adverse events: rash (9% vs. 20%), hyperglycemia (5% vs. 30%), diarrhea (5% vs. 10%)]. CONCLUSIONS: Capivasertib demonstrated clinically meaningful activity in heavily pretreated patients with AKT1 E17K-mutant ER+ MBC, including those with prior disease progression on fulvestrant. Tolerability and activity appeared improved by the combination.

A Randomized, Open-label, Presurgical, Window-of-Opportunity Study Comparing the Pharmacodynamic Effects of the Novel Oral SERD AZD9496 with Fulvestrant in Patients with Newly Diagnosed ER+ HER2- Primary Breast Cancer.

PURPOSE: Fulvestrant, the first-in-class selective estrogen receptor (ER) degrader (SERD), is clinically effective in patients with ER+ breast cancer, but it has administration and pharmacokinetic limitations. Pharmacodynamic data suggest complete ER degradation is not achieved at fulvestrant's clinically feasible dose. This presurgical study (NCT03236974) compared the pharmacodynamic effects of fulvestrant with AZD9496, a novel, orally bioavailable, nonsteroidal, potent SERD, in treatment-naïve patients with ER+ HER2- primary breast cancer awaiting curative intent surgery. PATIENTS AND METHODS: Patients were randomized 1:1 to receive AZD9496 250 mg twice daily from day 1 for 5-14 days, or fulvestrant 500 mg on day 1. On-treatment imaging-guided core tumor biopsies were taken between day 5 and 14 and compared with pretreatment diagnostic biopsies. The primary objective was to compare the effects of AZD9496 and fulvestrant on ER expression. Secondary objectives included changes in progesterone receptor (PR) and Ki-67 pharmacokinetic/pharmacodynamic relationships and safety. RESULTS: Forty-six women received treatment (AZD9496 n = 22; fulvestrant n = 24); 35 paired biopsies were evaluable (AZD9496 n = 15; fulvestrant n = 20). The least square mean estimate for ER H-score reduction was 24% after AZD9496 versus 36% after fulvestrant treatment (P = 0.86). AZD9496 also reduced PR H-scores (-33.3%) and Ki-67 levels (-39.9%) from baseline, but was also not superior to fulvestrant (PR: -68.7%, P = 0.97; Ki-67: -75.4%, P = 0.98). No new safety findings were identified. CONCLUSIONS: This was the first presurgical study to demonstrate that an oral SERD affects its key biological targets. However, AZD9496 was not superior to fulvestrant at the dose tested.

A Phase I Open-Label Study to Identify a Dosing Regimen of the Pan-AKT Inhibitor AZD5363 for Evaluation in Solid Tumors and in PIK3CA-Mutated Breast and Gynecologic Cancers.

Purpose: This phase I, open-label study (Study 1, D3610C00001; NCT01226316) was the first-in-human evaluation of oral AZD5363, a selective pan-AKT inhibitor, in patients with advanced solid malignancies. The objectives were to investigate the safety, tolerability, and pharmacokinetics of AZD5363, define a recommended dosing schedule, and evaluate preliminary clinical activity.Experimental Design: Patients were aged ≥18 years with World Health Organization (WHO) performance status of 0 to 1. Dose escalation was conducted within separate continuous and intermittent [4 days/week (4/7) or 2 days/week (2/7)] schedules with safety, pharmacokinetic, and pharmacodynamic analyses. Expansion cohorts of approximately 20 patients each explored AZD5363 activity in PIK3CA-mutant breast and gynecologic cancers.Results: MTDs were 320, 480, and 640 mg for continuous (n = 47), 4/7 (n = 21), and 2/7 (n = 22) schedules, respectively. Dose-limiting toxicities were rash and diarrhea for continuous, hyperglycemia for 2/7, and none for 4/7. Common adverse events were diarrhea (78%) and nausea (49%) and, for Common Terminology Criteria for Adverse Events grade ≥3 events, hyperglycemia (20%). The recommended phase II dose (480 mg bid, 4/7 intermittent) was assessed in PIK3CA-mutant breast and gynecologic expansion cohorts: 46% and 56% of patients, respectively, showed a reduction in tumor size, with RECIST responses of 4% and 8%. These responses were less than the prespecified 20% response rate; therefore, the criteria to stop further recruitment to the PIK3CA-mutant cohort were met.Conclusions: At the recommended phase II dose, AZD5363 was well tolerated and achieved plasma levels and robust target modulation in tumors. Proof-of-concept responses were observed in patients with PIK3CA-mutant cancers treated with AZD5363. Clin Cancer Res; 24(9); 2050-9. ©2017 AACRSee related commentary by Costa and Bosch, p. 2029.