A multi-institutional phase II study of SU101, a platelet-derived growth factor receptor inhibitor, for patients with hormone-Refractory prostate cancer

In a multi-institutional Phase II trial, we evaluated the efficacy of a platelet-derived growth factor receptor (PDGF-r) inhibitor, SU101, in patients with hormone-refractory prostate cancer. The patients received a 4-day i.v. loading dose of SU101 at 400 mg/m² for 4 consecutive days, followed by 10 weekly infusions at 400 mg/m². The primary study end points were a decline in prostate-specific antigen (PSA) and a decrease in measurable tumor. Secondary end points were time to progression and an effect on pain as measured by the Brief Pain Survey. Expression of PDGF-r was examined in both metastatic and archival primary prostate tumor samples. Forty-four patients were enrolled at four centers. The median age was 72 years, the median PSA was 223 ng/ml, and 21 patients had at least one prior chemotherapy. Thirty-nine patients are evaluable for PSA, and three patients demonstrated a PSA decline >50% from baseline (55-99.9% decrease). The median time to progression was 90 days. Of 19 patients evaluable for measurable disease, 1 patient had a partial response. Nine of 35 evaluable patients had significant improvement in pain. The most frequent adverse events were asthenia (75%), nausea (55%), anorexia (50%), and anemia (41%). PDGF-r expression was detected in 80% of the metastases and 88% of primary prostate cancers. The results of this trial may warrant further clinical studies with other PDGF-r inhibitors.