While new data from Arcus Biosciences Inc. and Gilead Sciences Inc. didn't do much to calm an unsteady development corridor, researcher, developers and analysts still hold out hope for the TIGIT pathway. The Arcus-Gilead randomized phase II study combining anti-TIGIT domvanalimab and anti-PD1 antibodies for treating first-line, metastatic non-small-cell lung cancer produced positive results, including improvements in median progression-free survival (PFS) and six-month landmark PFS rates vs. monotherapy. But a hefty dent in Arcus' shares provide a reminder of TIGIT’s fragility as a field, and a reminder of the phase III failure in May for Roche Holding AG unit Genentech Inc.'s anti-TIGIT immunotherapy tiragolumab, which dragged down the share value of several other class entrants. Arcus stock (NASDAQ:RCUS) dipped deeply on Dec. 20 on the new data’s release, but rallied on Dec. 21 by closing 7.5% upward at $22.15 each.