Experimental nitric oxide-donating glaucoma treatment "effective", but Pfizer drops it

PF-03187207, an experimental glaucoma treatment that was being developed by NicOx and Pfizer, has been shown in Phase II testing to be more effective in lowering IOP under certain circumstances than Pfizer's Xalatan (latanoprost) 0.005%, but it will not be advanced into Phase III testing, Pfizer has announced.

The randomized, double-masked dose-finding study enrolled 215 patients with primary open-angle glaucoma or ocular hypertension in at least one eye. In one study arm, subjects were treated for 28 days with Xalatan 0.005% either in the morning or the evening. The remaining five study arms treated subjects - in the morning, evening or both - with various doses of PF-03187207, a nitric oxide-donating prostaglandin analogue. IOP was measured at baseline, again at 8am, 10am, 1pm and 4pm on day one, and again once a week thereafter, on days seven, 14, 21 and 28.

The Phase II trial, comparing safety and efficacy of Xalatan with PF-03187207, did not achieve its primary endpoint of clinically statistical significance of PF-03187207 over Xalatan: the difference achieved between the two treatments was found to be approximately 1 mmHg - a difference of only 12%. No serious adverse events were noted. However, evening dosing of PF-03187207 was found to produce a statistically significant improvement (1.4 mmHg; 22%) over evening administration of Xalatan.

Although the companies believe that the nitric oxide donation has proved to be beneficial, Pfizer and NicOx will not be proceeding to Phase III testing of PF-03187207. Follow-up compounds are now being developed. PF-03187207 is still in Phase II testing in Japan, and Pfizer has announced that it would consider registering the product in the Asian market, depending on the results of trials, which are expected in the third quarter of this year.