The insulin-like growth factor-I receptor inhibitor figitumumab (CP-751,871) in combination with docetaxel in patients with advanced solid tumours: results of a phase Ib dose-escalation, open-label study

BACKGROUND: This phase Ib trial assessed safety, tolerability, and maximum tolerated dose (MTD) of figitumumab (CP-751,871), a fully human monoclonal antibody targeting the insulin-like growth factor type 1 receptor (IGF-IR), in combination with docetaxel. METHODS: Patients with advanced solid tumours were treated with escalating dose levels of figitumumab plus 75 mg m(–2) docetaxel every 21 days. Safety, efficacy, pharmacokinetics (PKs), and biomarker responses were evaluated. RESULTS: In 46 patients, no dose-limiting toxicities were attributable to the treatment combination. Grade 3 and 4 toxicities included neutropaenia (n=28), febrile neutropaenia (n=11), fatigue (n=10), leukopaenia (n=7), diarrhoea (n=5), hyperglycaemia, lymphopaenia, cellulitis, DVT, and pain (all n=1). The MTD was not reached. Four partial responses were observed; 12 patients had disease stabilisation of ⩾6 months. Pharmacokinetic and biomarker analyses showed a dose-dependent increase in plasma exposure, and complete sIGF-IR downregulation at doses of ⩾3 mg kg(–1). Pharmacokinetics of docetaxel in combination was similar to when given alone. Out of 18 castration-resistant prostate cancer patients, 10 (56%) had ⩾5 circulating tumour cells (CTCs) per 7.5 ml of blood at baseline: 6 out of 10 (60%) had a decline from ⩾5 to <5 CTCs and 9 out of 10 (90%) had a ⩾30% decline in CTCs after therapy. CONCLUSIONS: Figitumumab and docetaxel in combination are well tolerated. Further evaluation is warranted.