Avalanche Biotechnologies Inc. plans to acquire privately held Annapurna Therapeutics SAS through an all-stock transaction that will combine pipelines, management teams and resources with the goal of creating a gene therapy company that’s bigger than the sum of its parts. What remains to be seen is whether the deal can reverse the slide that has plagued Avalanche since the Menlo Park, Calif.-based company disappointed investors last year with phase IIa results of AVA-101 in wet age-related macular degeneration (AMD), despite the fact that data met the study’s 12-month safety endpoint.