Although the FDA has approved five biosimilars of Regeneron Pharmaceuticals, Inc.’s best-selling Eylea (aflibercept), patent infringement lawsuits by the drugmaker have kept those competitors off the U.S. market — until now. Following a successful defense of its Pavblu (aflibercept-ayyh), Amgen Inc. recently launched the drug at risk. The agent is entering an increasingly crowded therapeutic class, but it’s one that’s also costly for payers, which may be seeking some savings, say industry experts.