A third child with X-linked myotubular myopathy (XLMTM) has died after receiving the higher of two doses of an experimental gene therapy for the rare disease under development at Audentes Therapeutics Inc. Preliminary findings indicate that the immediate cause of death was gastrointestinal bleeding, Audentes said. The trial, testing AT-132 (resamirigene bilparvovec), was already on an FDA clinical hold.