Optimizing Early-stage Clinical Pharmacology Evaluation to Accelerate Clinical Development of Giredestrant in Advanced Breast Cancer.

PURPOSE: We describe the clinical pharmacology characterization of giredestrant in a first-in-human study. EXPERIMENTAL DESIGN: This phase Ia/Ib dose-escalation/-expansion study (NCT03332797) evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of giredestrant in estrogen receptor-positive HER2-negative locally advanced/metastatic breast cancer. The single-agent dose-escalation stage evaluated giredestrant 10, 30, 90, or 250 mg once daily. The dose-expansion stage evaluated single-agent giredestrant at 30, 100, and 250 mg once daily. Dose-escalation and -expansion phases also evaluated giredestrant 100 mg combined with palbociclib 125 mg. RESULTS: Following single-dose oral administration, giredestrant was rapidly absorbed and generally showed a dose-proportional increase in exposure at doses ranging from 10 to 250 mg. At the 30 mg clinical dose, maximum plasma concentration was 266 ng/mL (50.1%) and area under the concentration-time curve from 0 to 24 hours at steady state was 4,320 ng·hour/mL (59.4%). Minimal giredestrant concentrations were detected in urine, indicating that renal excretion is unlikely to be a major elimination route for giredestrant. Mean concentration of 4beta-hydroxycholesterol showed no apparent increase over time at both the clinical dose (30 mg) and a supratherapeutic dose (90 mg), suggesting that giredestrant may have low CYP3A induction potential in humans. No clinically relevant drug-drug interaction was observed between giredestrant and palbociclib. Giredestrant exposure was not affected by food and was generally consistent between White and Asian patients. CONCLUSIONS: This study illustrates how the integration of clinical pharmacology considerations into early-phase clinical trials can inform the design of pivotal studies and accelerate oncology drug development. SIGNIFICANCE: This work illustrates how comprehensive clinical pharmacology characterization can be integrated into first-in-human studies in oncology. It also demonstrates the value of understanding clinical pharmacology attributes to inform eligibility, concomitant medications, and combination dosing and to directly influence late-stage trial design and accelerate development.

Discovery of a novel series of potent and orally bioavailable phosphoinositide 3-kinase γ inhibitors.

The phosphoinositide 3-kinases (PI3Ks) have been linked to an extraordinarily diversified group of cellular functions making these enzymes compelling targets for the treatment of disease. A large body of evidence has linked PI3Kγ to the modulation of autoimmune and inflammatory processes making it an intriguing target for drug discovery. Our high-throughput screening (HTS) campaign revealed two hits that were nominated for further optimization studies. The in vitro activity of the first HTS hit, designated as the sulfonylpiperazine scaffold, was optimized utilizing structure-based design. However, nonoptimal pharmacokinetic properties precluded this series from further studies. An overlay of the X-ray structures of the sulfonylpiperazine scaffold and the second HTS hit within their complexes with PI3Kγ revealed a high degree of overlap. This feature was utilized to design a series of hybrid analogues including advanced leads such as 31 with desirable potency, selectivity, and oral bioavailability.