NEW YORK — Although the optimal dosing of anti-VEGF therapy remains unknown, pharmacokinetics of the two most popular agents suggest that adjusting the current dosing strategies may better serve patient needs.

Head-to-head trials of Lucentis (ranibizumab, Genentech) and Avastin (bevacizumab, Genentech) should help steer future treatment decisions, Philip J. Rosenfeld, MD, PhD, said during the J. Donald M. Gass Award Lecture, sponsored by the Retina Society, here at the Retina Congress 2009.

Yet, despite the absence of definitive clinical trials at the present time, there is suggestive evidence that either shortening the dosing frequency to 2 weeks, at least during the loading phase, or increasing the dose strength may result in significantly improved biological activity, Dr. Rosenfeld said.

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Ranibizumab has a 5- to 20-fold higher binding affinity than bevacizumab, and bevacizumab has a longer half-life than ranibizumab; correspondingly, studies have shown that ranibizumab has greater biological activity on day 0 than bevacizumab.

"But it's not how we start the month, it's how we finish the month," Dr. Rosenfeld said.

Studies of decay kinetics suggest similar activity of the two agents out to 30 days. However, Dr. Rosenfeld said, increasing either the dosing strength or dosing frequency of ranibizumab or bevacizumab, provided it is safe, would yield significantly higher biological activity at 30 days.

A novel anti-VEGF agent, VEGF Trap-Eye (Regeneron and Bayer), may convey even greater affinity and result in 450 times the amount of biological activity at the end of 1 month than either bevacizumab or ranibizumab.