In February, Belgian company Ablynx sealed a deal with Merck of Whitehouse Station, New Jersey, to co-develop several nanobody drugs directed at immune checkpoints to treat cancer. This and a flurry of recent deals, including Bristol-Myers Squibb's pact with Five Prime Therapeutics and Novartis' acquisition of CoStim, confirm the industry's infatuation with checkpoint modulators. “Merck wants in, too,” says Mick Cooper, a healthcare analyst at London–based Edison Investment Research, particularly after the approval of checkpoint inhibitor Yervoy (ipilimumab). “Ablynx is enabling Merck to potentially have products that could be differentiated from others,” Cooper says. Ablynx will receive €20 ($27) million in cash and up to €10.7 ($14.8) million to fund research over three years. The Ghent-based biotech is eligible to receive up to €1.7 ($2.3) billion in milestones and royalties. Immune checkpoints, such as PD-1, are involved in suppressing immunity so drugs that block these pathways can reactivate the immune response. Whereas most immune-checkpoint blockers in development are monoclonal antibodies (mAbs), nanobodies are fragments of llama antibodies based on a single monomeric variable antibody domain—and one-tenth the size of mAbs. Ablynx's platform links several nanobody proteins to form a molecule that can target more than one protein. “Most companies can't do that [with their technology],” Cooper says. The collaboration expands a €456 ($624)-million deal signed between the two companies in 2012 to discover drugs to modulate ion channel activity to treat neurological disease.