Nearly two years after Gilead Sciences Inc. spent $4.9 billion to buy Forty Seven Inc. and its lead candidate, magrolimab, the FDA clamped a partial clinical hold on five of Gilead’s clinical trials combining the therapy with azacitidine. The cause, according to Gilead’s management, is “an apparent imbalance in investigator-reported suspected unexpected serious adverse reactions between study arms.” The company said it has not identified a clear trend in the adverse reactions or new safety signals.