What happened?Following a progress report on Arcus Biosciences' most valuable asset, the shares of the clinical-stage biopharmaceutical firm are in the ascendant. The stock rose 14% on Thursday due to investors hoping Gilead Sciences will license Domvanalimab (NASDAQ:GILD).What are you waiting for?Gilead Sciences and Arcus Biosciences signed an agreement for a 10-year period to co-develop, co-commercialize and market a few of Arcus Biosciences next-generation cancer treatments. Gilead Sciences has the option to pay Arcus $275million for exclusive rights to Domvanalimab (one of many anti-Tigit antibody in clinical-stage testing).The theory is that tumors will be able to hide their identity from the immune system by inhibiting Tigit. Arcus Biosciences' early clinical trials suggest that anti-Tigit drugs can be combined with other immunotherapies to increase their effectiveness.Since Roche (OTC.RHHBY), shared compelling data about a new anti-Tigit antibody called tiragolumab, there has been a lot of interest in the subject. Tiragolimusb and Tecentriq combined with tiragolumab reduced the size of tumors in 31% of lung cancer patients, compared to 16% who received Tecentriq alone.Arcus Biosciences stock gained today but not much for a biotech with a promising late-stage pipeline. The reason is that the company has been unusually cautious about disclosing key information from the ongoing Arc-7 study.What now?Arcus Biosciences praised the response rate data, but declined to disclose the exact percentages. Positive data is never kept secret by clinical-stage biotechnology companies. Therefore, today's nondisclosure should alarm alarm bells.According to the company, patients who received zimberelimab (an experimental PD-1 inhibitor) as a monotherapy performed equally well as those who received Tecentriq or similar immunotherapies in the exact same setting. Investors must assume that adding domvanalimab and zimberelimab did not increase patient response rates.Gilead Sciences will not exercise its option to fully licence domvanalimab despite Arcus Biosciences's disturbing nondisclosure today. It doesn't seem possible, however, without high response rates.
