First-in-human study of the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of PF-00299804, a small molecule irreversible panHER inhibitor in patients with advanced cancer

Abstract

3599 Background: There are scientific rationale for inhibitors which provide combined and irreversible blockade of HER family members. PF-00299804 is an orally available, potent, irreversible small molecule inhibitor of the HER tyrosine kinases. Methods: The safety, tolerability, PK, PD, and efficacy of PF-00299804 administered orally once daily in 3-week cycles were assessed in patients with advanced solid tumors using an accelerated dose-escalation design. Safety assessments included adverse event (AE), laboratory, ECG, and LVEF assessments. PK parameters were determined after a single lead-in dose and on Day 14 by non-compartmental techniques. PD measures included assessment of HER-related signaling pathways via IHC analyses of serial skin and, in some patients, tumor biopsies. Serial 18F-FDG- PET/CT has been performed on a subset of patients with scans being classified according to modified EORTC criteria by a central reader. Results: 32 pts have been treated across 8 sequential dose levels ranging from 0.5 to 60 mg. The most common AEs were diarrhea, fatigue, nausea, and rash. 3/6 patients at 60 mg experienced a DLT [hand-foot syndrome (1), dehydration related to diarrhea(1), mucositis(1)]. Cmax and AUC of PF-00299804 increased with dose in an approximately proportional manner. Accumulation ranged from 3.3 to 6.8, suggesting a terminal t1/2>24 h. At the 30 mg dose level, mean Day 14 drug concentration was above the predicted efficacious concentration for tumor growth inhibition based on A431 xenograft model. Of 7 sets of PET data evaluated thus far, partial responses (PR) have been observed in 2 patients. A PR as assessed using RECIST criteria has been reported in 1 of 2 patients with advanced refractory NSCLC treated to date. Conclusions: Daily administration of PF-00299804 across many dose levels appears safe and tolerable. Diarrhea, fatigue, nausea, and rash are the most frequent AEs. Evaluation of 45 mg/d as the potential MTD is ongoing. Systemic exposures at doses = 30 mg exceed the threshold for efficacy as predicted from preclinical studies. Clinical and biological activity of PF-00299804 was observed including a PR in 1 of 2 patients with advanced refractory NSCLC. No significant financial relationships to disclose.