Figitumumab + docetaxel in treatment of CRPC

Figitumumab (also known as CP-751,871) is a fully humanized monoclonal antibody designed to target the insulin-like growth factor type 1 receptor (IGF-IR). Data are now available from a very early-stage trial of figitumumab in combination with docetaxel in the treatment of patients with late-stage solid tumors — including castration-resiatant prostate cancer (CRPC).

Molife et al. have reported data from a Phase Ib trial designed to assess the safety, the tolerability, and the maximum tolerated dose (MTD) of figitumumab when used to treat patients with advanced solid tumors in combination with docetaxel. A total of 46 patients with several types of cancer were treated with gradually increasing dose levels of figitumumab plus 75 mg/m2 docetaxel every 21 days.

The trial included 18 patients with CRPC. Results of this regimen in those patients were as follows:

  • 10/18 patients with CRPC (56 percent) had ≥ 5 circulating tumour cells (CTCs) per 7.5 ml of blood at baseline.
  • 6/10 patients with CRPC (60 percent) had a reduction in their CTC level from ≥ 5 to < 5 CTCs.
  • For 9 /10 patients with CRPC who had a reduction in their CTCs (90 percent), that reduction was ≥ 30 percent  post-therapy.
  • The MTD of figitumumab was not reached in this trial.

In the entire series of 46 patients, there were no dose-limiting toxicities attributable to the treatment combination. Grade 3 and 4 toxicities included neutropenia (n = 28), febrile neutropenia (n = 11), fatigue (n = 10), leucopenia (n = 7), diarrhea (n = 5), hyperglycemia, lymphopenia, cellulitis, deep vein thrombosis, and pain (all, n = 1).

According to the authors, the combination of figitumumab and docetaxel appears to be well tolerated, despite the grade 3 and 4 toxicities mentioned above. Additional trials will be neccessary, however, before figitumumab can be tested in a large, randomized, Phase III, double -blind trial. As yet there is no sign of a Phase II clinical trial of figitumumab in CRPC, despite the above data.

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