* 53 had complete or partial shrinkage of bone lesions
* 8 patients had stable disease
By Deena Beasley
LOS ANGELES, Feb 17 (Reuters) - Exelixis Inc’s (EXEL.O) experimental cancer drug cabozantinib has been shown in a mid-stage trial to completely or partially clear up bone lesions from prostate cancer in 85 percent of patients, according to research presented on Thursday.
Of 62 patients evaluated by bone scan, 53 had either complete or partial shrinkage of metastatic bone lesions, which can lead to bone fractures, severe pain and eventual death. Eight other patients, or 13 percent, had stable disease. The disease worsened in one patient.
In addition, the interim results show that tumors shrank in 61 of the 91 patients with cancer that had spread to soft tissue, including the liver and lungs.
The drug was also shown to reduce bone pain as well as the need for narcotic painkillers, and to increase hemoglobin in patients with anemia, according to the company.
Exelixis said 168 patients were enrolled in the trial, for which full results will be reported in June.
After 12 weeks of treatment, some patients were randomized to either placebo or cabozantinib, but the trial was eventually unblinded when it became clear that the drug was effective.
At a follow-up of 3.8 months, patients on placebo lived for a median of 40 days without their disease worsening. A comparable number for cabozantinib-treated patients is not yet available because 79 pct of them have not had disease progression and are still receiving the drug.
Patients in the Phase 2 trial suffered from castration-resistant prostate cancer, meaning their tumor had stopped responding to hormone deprivation therapy.
Cabozantinib, also known as XL184, is an oral drug designed to block the vascular endothelial growth factor, the same target as drugs like Roche Holding AG’s ROG.VX Avastin, as well as MET and RET, two other drivers of tumor formation.
Side effects seen in the trial included fatigue, high blood pressure, back pain and hand foot syndrome, a side effect of chemotherapy causing redness and peeling in the palms and soles of the feet.
Cabozantinib is being studied as a treatment for thyroid cancer, glioblastoma and other solid tumors.
Editing by Bernard Orr