In a deal worth at least US$695 M, Merck & Co. has partnered up with Dragonfly Therapeutics to develop and commercialise natural killer (NK) cell engager therapies for the treatment of solid tumour indications. This follows positive interim Phase Ib data from Merck’s 2016 collaboration with Affimed, in which Keytruda® (pembrolizumab) and AFM13, a bispecific NK cell engager, in combination produced an 89% response rate compared to monotherapy. For Dragonfly, the deal comes over a year after Celgene bought into the technology, with a five-year agreement for up to four candidates to treat haematological cancers.