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 pla telet-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/m(2) for 4 consecutive days, followed by TO weekly infusions at 400 mg/m2. The primary study end points were a decli ne in prostate-specific antigen (PSA) and a decrease in measurable tumor. S econdary end points were time to progression and an effect on pain as measu red by the Brief Pain Survey, Expression of PDGF-r was examined in both met astatic and archival primary prostate tumor samples. Forty-four patients we re enrolled at four centers, The median age was 72 years, the median PSA wa s 223 ng/ml, and 21 patients had at least one prior chemotherapy, Thirty-ni ne patients are evaluable for PSA, and three patients demonstrated a PSA de cline >50% from baseline (55-99.9% decrease). The median time to progressio n was 90 days, Of 19 patients evaluable for measurable disease, 1 patient h ad a partial response. Nine of 35 evaluable patients had significant improv ement 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 inhibitor s.