Preclinical and Clinical Studies With the Multi-Kinase Inhibitor CEP-701 as Treatment for Prostate Cancer Demonstrate the Inadequacy of PSA Response as a Primary Endpoint

Connie Collins, Michael A. Carducci, Mario A. Eisenberger, John T. Isaacs, Alan W. Partin, Roberto Pili, Victoria J. Sinibaldi, Janet S. Walczak and Samuel R. Denmeade

volume 6 | issue 9

September 2007
Pages: 1360 - 1367

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PURPOSE: CEP-701 is a potent inhibitor of trk receptors that causes cell death in prostate cancer (PC) models. CEP-701 binds to serum proteins and a preprostatectomy study was performed to assess prostate tissue penetration and clinical response to CEP-701.

METHODS: Growth assays and western blot analyses were performed to evaluate CEP-701 kinase inhibition. In a preprostatectomy study, patients received CEP-701 for five days prior to prostatectomy and prostate tissue analyzed for CEP-701 levels. A phase II dose escalation study was performed in patients with hormone refractory PC with rising PSA and no metastases. Endpoints included PSA response and safety.

RESULTS: CEP-701 binds to serum proteins limiting tissue penetration. An oral dose of 40 mg bid of CEP-701 for five days produced levels of 219 ± 38 nM in prostate at time of prostatectomy. No patients in the Phase II study met the primary response criteria of > 50% PSA decline. 7/9 patients had increase in PSA slope on CEP-701 compared to PSA slope prestudy. 5/9 patients had a decrease in PSA levels after stopping CEP-701. Laboratory studies showed increased PSA production by CEP-701 growth arrested human PC cells in vitro and in vivo.

CONCLUSIONS: Evaluation of PSA response is an inadequate indicator of response in CEP-701 treated PC patients. Therefore, the effectiveness of CEP-701 as treatment for prostate cancer has not been adequately tested. Based on a strong preclinical rationale, further clinical studies with CEP-701 using alternative endpoints are indicated.