Shares of Ionis Pharmaceuticals (NASDAQ: IONS) and Biogen (NASDAQ: BIIB) lost at least 2% in market cap on Thursday after the companies announced their decision to terminate the development of their investigational amyotrophic lateral sclerosis (ALS) drug, BIIB105 / ION541. This decision was based on topline data from the phase I/II ALSpire study, wherein treatment with the drug did not slow disease progression. This was evident from the six-month data from the study wherein ALS patients treated with BIIB105 did not achieve a reduction in levels of plasma neurofilament light chain (NfL), a marker of neurodegeneration and neuronal damage. Patients treated with BIIB105 also failed to demonstrate an impact on clinical outcome measures of function, breathing and strength. However, this wasn't the only partnership with Ionis that Biogen walked away from. In a separate press release, the pharma giant announced its decision to opt out of licensing the rights to develop BIIB121 / ION582, an experimental Angelman Syndrome drug. However, Biogen did not specify any rationale for this decision. Year to date, shares of Biogen are down 11.1% compared to the industry‘s 4.6% fall. Image Source: Zacks Investment Research Despite Biogen's departure, Ionis intends to advance ION582 independently as part of its wholly-owned pipeline. In ...