To add a somewhat cynical view, a significant part of the original motivation for the ranibizumab (Lucentis) development was due to pricing arbitrage across diseases. bevicizumab was priced based on uses in cancer indications with a “large” volume (many mls) used for systemic infusion. The same product injected into the eye, in say a 1:1000 volume, could be efficacious for AMD, but pricing per volume would be trivial amount at the bevi cost per volume. So they tweaked the active ingredient to a new product (exact same mechanism ) and raised the price per volume to a market standard cost per treatment. There may be some pk-type benefits to the derivative , but the pricing context is an industry case study.