Early results with tanezumab (RN624), an investigational monclonal antibody against nerve growth factor, show promise for chronic bladder pain in interstitial cystitis.
The phase IIa proof of concept study was aimed at assessing the efficacy and safety of single-dose tanezumab, 200 micrograms/kg, in treating IC. The monoclonal antibody drug, given as a one-time infusion, produced clinically significant reductions in pain at week 6 in tanezumab-treated patients versus those on placebo. All patients enrolled in the study had moderate to severe IC, with scores of at least 13 on the Pelvic Pain and Urgency/Frequency scale and at least 7 on the O'Leary-Sant Interstitial Cystitis Symptom Index.
Patients were able to continue their usual medications during the study with the exception of bladder instillations, noted study co-author Robert J. Evans III, MD, a urologist with Alliance Urology Specialists in Greensboro, NC.
Patients are 'significantly better'
"We had a lot of 8s, 9s, 10s," Dr. Evans told Urology Times. "They really felt like they were significantly better."
Side effects were minimal, Dr. Evans said. The most common adverse event was headache (in five placebo patients and seven tanezumab patients). Second most common were paresthesias, occurring in one placebo patient and six tanezumab patients. These were mostly some tingling in the feet, Dr. Evans noted. There were two serious adverse events in tanezumab patients, with one patient reporting vertigo and another reporting drug exposure during pregnancy.
There were no mental status or coordination problems and no confirmed evidence of new or worsened peripheral neuropathy, Dr. Evans said.
Pfizer, the drug's maker, is working with investigators to determine the next steps in the development program for IC. One of the challenges, Dr. Evans noted, will be enrolling patients with high pain scores who are not using a lot of oral pain medication and who are not using bladder instillations.
Tanezumab is currently still in clinical development and its potential cost has yet to be determined. However, if tanezumab was to reach the marketplace, based on other monoclonal antibody agents used to treat rheumatoid arthritis and Crohn's disease, it may be costly.
"But if you get great results with it and can eliminate a lot of other medications, the cost may not be so bad," Dr. Evans pointed out.
Other symptoms may need treatment
IC patients' other symptoms may still need treatment, however.
"Those of us who treat a lot of IC feel there are still end-organ issues-particularly with the glycosaminoglycan layer and mast cells-but if we could help roll back the neuropathic part of their pain, it can give us another tool to manage IC," said Dr. Evans.
Urologists will likely hear more about results with tanezumab at the European Association of Urology annual meeting next April and the AUA annual meeting next May, he said.
The trial was sponsored by Pfizer.