Background: BIBF 1120 is an oral, potent, tyrosine kinase inhibitor that simultaneously targets vascular endothelial growth factor receptors 1-3, platelet-derived growth factor receptors α and β, and fibroblast growth factor receptors 1-3, as well as FLT3 and Src. Currently, the molecule is in phase III development for second-line non-small cell lung cancer and first-line ovarian cancer patients.
Methods: This phase I dose-escalation study assessed the safety and maximum tolerated dose of continuous daily treatment with BIBF 1120 plus standard-dose docetaxel (75 mg m(-2), every 3 weeks) and prednisone (5 mg BID) in patients with metastatic, chemo-naive, hormone-refractory prostate cancer (HRPC). Secondary objectives were characterisation of BIBF 1120 and docetaxel pharmacokinetics (PK), and preliminary antitumour activity.
Results: Patients received BIBF 1120 100 mg BID (n=3), 150 mg BID (n=3), 200 mg BID (n=3), and 250 mg BID (n=12). The most frequent drug-related adverse events were diarrhoea (71.4%), asthenia (61.9%), nausea (28.6%), vomiting (28.6%), and alopecia (23.8%). The maximum tolerated dose was 250 mg BID of BIBF 1120. Overall, reversible grade 3/4 liver enzyme elevations occurred in six of twelve patients at this dose level. Among 19 assessable patients, 13 (68.4%) showed a ≥50% reduction in prostate serum antigen levels from baseline and among 6 evaluable patients with measurable lesions 1 patient experienced a partial response by Response Evaluation Criteria In Solid Tumours criteria. Pharmacokinetic analysis showed no interactions between BIBF 1120 and docetaxel/prednisone.
Conclusion: Based on the overall safety profile, 200 mg BID was the recommended dose for the combination of BIBF 1120 with the standard dose of 75 mg m(-2) of docetaxel and prednisone that might be further investigated in HRPC patients. This combination was well tolerated, with preliminary signs of efficacy and no indication of PK interaction between BIBF 1120 and docetaxel.