Purpose Wee1 tyrosine kinase phosphorylates and inactivates cyclin-dependent kinase (Cdk) 1/2 in response to DNA damage. AZD1775 is a first-in-class inhibitor of Wee1 kinase with single-agent antitumor activity in preclinical models. We conducted a phase I study of single-agent AZD1775 in adult patients with refractory solid tumors to determine its maximum-tolerated dose (MTD), pharmacokinetics, and modulation of phosphorylated Tyr15-Cdk (pY15-Cdk) and phosphorylated histone H2AX (γH2AX) levels in paired tumor biopsies. Patients and Methods AZD1775 was administered orally twice per day over 2.5 days per week for up to 2 weeks per 21-day cycle (3 + 3 design). At the MTD, paired tumor biopsies were obtained at baseline and after the fifth dose to determine pY15-Cdk and γH2AX levels. Six patients with BRCA-mutant solid tumors were also enrolled at the MTD. Results Twenty-five patients were enrolled. The MTD was established as 225 mg twice per day orally over 2.5 days per week for 2 weeks per 21-day cycle. Confirmed partial responses were observed in two patients carrying BRCA mutations: one with head and neck cancer and one with ovarian cancer. Common toxicities were myelosuppression and diarrhea. Dose-limiting toxicities were supraventricular tachyarrhythmia and myelosuppression. Accumulation of drug (t1/2 approximately 11 hours) was observed. Reduction in pY15-Cdk levels (two of five paired biopsies) and increases in γH2AX levels (three of five paired biopsies) were demonstrated. Conclusion This is the first report of AZD1775 single-agent activity in patients carrying BRCA mutations. Proof-of-mechanism was demonstrated by target modulation and DNA damage response in paired tumor biopsies.

The Wee1 kinase inhibitor adavosertib abrogates cell cycle arrest, leading to cell death. Prior testing of twice-daily adavosertib in patients with advanced solid tumors determined the recommended phase 2 dose (RPh2D). Here, we report results for once-daily adavosertib.Patients and Methods: A 3 + 3 dose escalation design was used, with adavosertib given once daily on days 1-5 and 8-12 in 21-day cycles. Molecular biomarkers of Wee1 activity, including tyrosine 15-phosphorylated Cdk1/2 [pY15-Cdk]), were assessed in paired tumor biopsies.Whole-exome sequencing and RNA sequencing of remaining tumor tissue identified potential predictive biomarkers.Results: Among the 42 patients enrolled, the most common toxicities were gastrointestinal and hematological; dose-limiting toxicities were grade 4 hematological toxicity and grade 3 fatigue.The once-daily RPh2D was 300 mg. Six patients (14%) had confirmed partial responses (PR): 4 ovarian, 2 endometrial. Adavosertib plasma exposures were similar to those from twice-daily dosing. On cycle 1 day 8 (pre-dose), tumor pY15-Cdk levels were higher than baseline in 4 of 8 patients, suggesting target rebound during the day 5-8 dosing break. One patient who progressed rapidly had a tumor WEE1 mutation and potentially compensatory PKMYT1 overexpression.Baseline CCNE1 overexpression occurred in both of 2 responding patients, only 1 of whom had CCNE1 amplification, and in 0 of 3 non-responding patients. Conclusions:We determined the once-daily adavosertib RPh2D and observed activity in patients with ovarian or endometrial carcinoma, including 2 with baseline CCNE1 mRNA overexpression. Future studies will determine whether CCNE1 overexpression is a predictive biomarker for adavosertib.

Background Molecular chaperone targeting has shown promise as a therapeutic approach in human cancers of various histologies and genetic backgrounds. The purine-scaffold inhibitor PU-H71 (NSC 750424), selective for Hsp90 in epichaperome networks, has demonstrated antitumor activity in multiple preclinical cancer models. The present study was a first in-human trial of PU-H71 aimed at establishing its safety and tolerability and characterizing its pharmacokinetic (PK) profile on a weekly administration schedule in human subjects with solid tumors refractory to standard treatments. Methods PU-H71 was administered intravenously over 1 h on days 1 and 8 of 21-day cycles in patients with refractory solid tumors. Dose escalation followed a modified accelerated design. Blood and urine were collected during cycles 1 and 2 for pharmacokinetics analysis. Results Seventeen patients were enrolled in this trial. Grade 2 and 3 adverse events were observed but no dose limiting toxicities occurred, thus the human maximum tolerated dose was not determined. The mean terminal half-life (T) was 8.4 ± 3.6 h, with no dependency to dose level. A pathway for the metabolic disposal of PU-H71 in humans was derived from microsome studies. Fourteen patients were also evaluable for clinical response; 6 (35%) achieved a best response of stable disease for >2 cycles, with 2 patients remaining on study for 6 cycles. The study closed prematurely due to discontinuation of drug supply. Conclusions PU-H71 was well tolerated at the doses administered during this study (10 to 470 mg/m/day), with no dose limiting toxicities.