As reported in the primary analysis, tiragolumab plus atezolizumab had a tolerable safety profile, Dr. Johnson said.
“Despite a near doubling of the median treatment duration [at the updated analysis], there were similar numbers of any-cause adverse events, grade 3-5 adverse events, and serious adverse events,” she said.
Overall, adverse events occurred in 99% of patients in the tiragolumab arm and 96% of those in the placebo arm. Rates of grade 3-5 adverse events were 48% and 44%, respectively. Rates of serious adverse events were 37% and 35%, respectively.
A higher frequency of adverse events in the tiragolumab arm was related to an increase in immune-related events, including infusion reactions, pruritus, rash, arthralgia, and nephritis. This makes sense because the patients in that group were receiving two active immunotherapies, Dr. Johnson said.
Data inspire cautious optimism
The safety and activity of tiragolumab plus atezolizumab are “to be confirmed in an ongoing phase 3 study called SKYSCRAPER-01 ,” Dr. Johnson said.
Invited discussant, of Roswell Park Comprehensive Cancer Center in Buffalo, N.Y., said the ORRs in CITYSCAPE have “generated a lot of buzz,” but she urged caution pending phase 3 results.
“While we are all excited by the data and want to see a winner, we should be careful, as speed can also crash and burn,” she said. “We have plenty of examples of promising studies that collapsed in later phase trials.”
There is room, however, for cautious optimism that the combination is a promising advance “as long as no prognostic or confounding variable is determined later on to be nonrandomly distributed between the groups to account for the difference seen,” Dr. Dy said.
She also noted that “the distribution of favorable or unfavorable mutations between the groups is unknown, and understanding this will be relevant.”
Preclinical data suggest the presence of DNM1 expression is crucial for maximizing the effect of TIGIT blockade, and tumor MHC class 1 expression appears to be reduced alongside reductions in DNM1 expression in the intratumoral natural kill cells in lung cancer specimens, Dr. Dy explained.
“Assessment of these biomarkers will be instructive,” she said. “More recent data also appear to implicate a paradoxical role of soluble CD155 or PVR ligand in actually inhibiting DNM1, so the effect of systemic TIGIT blockade may be mitigated if there is rebound increase of counterbalancing signals by increased secretion of soluble CD155, and we look forward to more data in the future regarding this.”
CITYSCAPE was sponsored by Genentech. Dr. Johnson disclosed relationships with Genentech and numerous other companies. Dr. Dy disclosed relationships with AstraZeneca, GlaxoSmithKline, Takeda, Amgen, Bristol-Myers Squibb, Regeneron, and Tesaro.
SOURCE: Rodriguez-Abreu D et al. ASCO 2020, .