Seeking to increase its foothold in the emerging market for generic biologic drugs, Novartis committed to pay a Cambridge, Mass., biotech firm up to $263 million and collaborate on four drugs. As part of the accord between Sandoz — the generic unit of Novartis — and Momenta Pharmaceuticals, the two will develop three new product candidates, one from Momenta and two from Sandoz. The firms would not disclose them. The companies already collaborate on a generic version of Lovenox, a blood thinner from Sanofi-Aventis, for the US market, and the new agreement extends that pact to Europe. Sandoz agreed to make an initial payment of $75 million to Momenta for the purchase of a 13% stake in the biotech company. Momenta is eligible to receive up to $188 million in additional milestone payments. Biotech copycats are a key part of the growth strategy for Sandoz, which this year brought to market the first follow-on biologic—the Omnitrope human growth hormone. The partnership with Momenta aims to establish an approach to facilitate development and registration of generic versions of recombinant biotech drugs.