BEECH: a dose-finding run-in followed by a randomised phase II study assessing the efficacy of AKT inhibitor capivasertib (AZD5363) combined with paclitaxel in patients with estrogen receptor-positive advanced or metastatic breast cancer, and in a PIK3CA mutant sub-population.

BACKGROUND: BEECH investigated the efficacy of capivasertib (AZD5363), an oral inhibitor of AKT isoforms 1-3, in combination with the first-line weekly paclitaxel for advanced or metastatic estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer, and in a phosphoinositide 3-kinase, catalytic, alpha polypeptide mutation sub-population (PIK3CA+). PATIENTS AND METHODS: BEECH consisted of an open-label, phase Ib safety run-in (part A) in 38 patients with advanced breast cancer, and a randomised, placebo-controlled, double-blind, phase II expansion (part B) in 110 women with ER+/HER2- metastatic breast cancer. In part A, patients received paclitaxel 90 mg/m2 (days 1, 8 and 15 of a 28-day cycle) with capivasertib taken twice daily (b.i.d.) at two intermittent ascending dosing schedules. In part B, patients were randomly assigned, stratified by PIK3CA mutation status, to receive paclitaxel with either capivasertib or placebo. The primary end point for part A was safety to recommend a dose and schedule for part B; primary end points for part B were progression-free survival (PFS) in the overall and PIK3CA+ sub-population. RESULTS: Capivasertib was well tolerated, with a 400 mg b.i.d. 4 days on/3 days off treatment schedule selected in part A. In part B, median PFS in the overall population was 10.9 months with capivasertib versus 8.4 months with placebo [hazard ratio (HR) 0.80; P = 0.308]. In the PIK3CA+ sub-population, median PFS was 10.9 months with capivasertib versus 10.8 months with placebo (HR 1.11; P = 0.760). Based on the Common Terminology Criteria for Adverse Event v4.0, the most common grade ≥3 adverse events in the capivasertib group were diarrhoea, hyperglycaemia, neutropoenia and maculopapular rash. Dose intensity of paclitaxel was similar in both groups. CONCLUSIONS: Capivasertib had no apparent impact on the tolerability and dose intensity of paclitaxel. Adding capivasertib to weekly paclitaxel did not prolong PFS in the overall population or PIK3CA+ sub-population of ER+/HER2- advanced/metastatic breast cancer patients.ClinicalTrials.gov: NCT01625286.

Early ctDNA dynamics as a surrogate for progression-free survival in advanced breast cancer in the BEECH trial.

BACKGROUND: Dynamic changes in circulating tumour DNA (ctDNA) levels may predict long-term outcome. We utilised samples from a phase I/II randomised trial (BEECH) to assess ctDNA dynamics as a surrogate for progression-free survival (PFS) and early predictor of drug efficacy. PATIENTS AND METHODS: Patients with estrogen receptor-positive advanced metastatic breast cancer (ER+ mBC) in the BEECH study, paclitaxel plus placebo versus paclitaxel plus AKT inhibitor capivasertib, had plasma samples collected for ctDNA analysis at baseline and at multiple time points in the development cohort (safety run-in, part A) and validation cohort (randomised, part B). Baseline sample ctDNA sequencing identified mutations for longitudinal analysis and mutation-specific digital droplet PCR (ddPCR) assays were utilised to assess change in ctDNA abundance (allele fraction) between baseline and 872 on-treatment samples. Primary objective was to assess whether early suppression of ctDNA, based on pre-defined criteria from the development cohort, independently predicted outcome in the validation cohort. RESULTS: In the development cohort, suppression of ctDNA was apparent after 8 days of treatment (P = 0.014), with cycle 2 day 1 (4 weeks) identified as the optimal time point to predict PFS from early ctDNA dynamics. In the validation cohort, median PFS was 11.1 months in patients with suppressed ctDNA at 4 weeks and 6.4 months in patients with high ctDNA (hazard ratio = 0.20, 95% confidence interval 0.083-0.50, P < 0.0001). There was no difference in the level of ctDNA suppression between patients randomised to capivasertib or placebo overall (P = 0.904) nor in the PIK3CA mutant subpopulation (P = 0.071). Clonal haematopoiesis of indeterminate potential (CHIP) was evident in 30% (18/59) baseline samples, although CHIP had no effect on tolerance of chemotherapy nor on PFS. CONCLUSION: Early on-treatment ctDNA dynamics are a surrogate for PFS. Dynamic ctDNA assessment has the potential to substantially enhance early drug development. CLINICAL REGISTRATION NUMBER: NCT01625286.

A serine protease is involved in the initiation of DNA damage-induced apoptosis.

Caspases are considered to be the key effector proteases of apoptosis. Initiator caspases cleave and activate downstream executioner caspases, which are responsible for the degradation of numerous cellular substrates. We studied the role of caspases in apoptotic cell death of a human melanoma cell line. Surprisingly, the pancaspase inhibitor zVAD-fmk was unable to block cleavage of poly(ADP-ribose) polymerase (PARP) after treatment with etoposide, while it did prevent DEVDase activity. It is highly unlikely that caspase-2, which is a relatively zVAD-fmk-resistant caspase, is mediating etoposide-induced PARP cleavage, as a preferred inhibitor of this caspase could not prevent cleavage. In contrast, caspase activation and PARP degradation were blocked by pretreatment of the cells with the serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF). We therefore conclude that a serine protease regulates an alternative initiation mechanism that leads to caspase activation and PARP cleavage. More importantly, while zVAD-fmk could not rescue melanoma cells from etoposide-induced death, the combination with AEBSF resulted in substantial protection. This indicates that this novel pathway fulfills a critical role in the execution of etoposide-induced programmed cell death.

Secreted production of a custom-designed, highly hydrophilic gelatin in Pichia pastoris.

A custom-designed, highly hydrophilic gelatin was produced in Pichia pastoris. Secreted production levels in single-copy transformants were in the range 3-6 g/l of clarified broth and purification to near homogeneity could be accomplished by differential ammonium sulfate precipitation. Despite the fact that gelatins are highly susceptible to proteolysis because of their unfolded structure, the recombinant protein was shown to be fully intact by SDS-PAGE, N-terminal sequencing, gel filtration chromatography and mass spectrometry. Owing to its highly hydrophilic nature, the migration of the synthetic gelatin in SDS-PAGE was severely delayed. Esterification of the carboxylic amino acid side chains resulted in normal migration. The high polarity of the synthetic gelatin also accounts for its negligible surface activity in water at concentrations up to 5% (w/v), as determined by tensiometry. Circular dichroism spectrometry showed that the non-hydroxylated gelatin did not form triple helices at 4 degrees C. The spectrum was even more representative of the random coil conformation than the spectrum of natural non-hydroxylated gelatins.