TORCHLIGHT: A Randomized, Double-Blind, Phase III Trial of Toripalimab Versus Placebo, in Combination with Nab-Paclitaxel(nab-p) for Patients with Metastatic or Recurrent Triple-Negative Breast Cancer (TNBC)

Background: Checkpoint blockade combined with taxanes based chemotherapy had generated mixed results as first line treatment for metastatic TNBC. Toripalimab, a humanized IgG4K monoclonal antibody specific for PD-1, provided significant clinical efficacy with a favorable safety profile in various solid tumors. The purpose of this study is to compare the efficacy and safety of toripalimab versus placebo, in combination with nab-P for metastatic or recurrent TNBC (NCT04085276). Methods: Patients with initially diagnosed metastatic or recurrent inoperable TNBC were randomized 2:1 to receive toripalimab (240mg, D1, q3w) or placebo along with nab-P on days1, 8 in 3-week cycles. Stratifications included PD-L1 expression, paclitaxel therapy history and line of prior therapy at enrollment. Primary endpoint was progression-free survival (PFS) assessed by a blinded independent central review (BICR) per RECIST v1.1, first in the PD-L1-positive population and then in the ITT population. Secondary endpoints included overall survival (OS) and safety. Results: 531 patients were randomized to toripalimab (n = 353) or placebo (n = 178); 200 and 100 patients, respectively had PD-L1 positive TNBC. At interim analysis, with the median follow-up of 14 months, a statistically significant improvement in PFS by BICR was demonstrated for the toripalimab arm in the PD-L1 positive subgroup (mPFS 8.4 vs 5.6 months; HR = 0.653, 95% CI 0.470-0.906, P = 0.0102). The PFS in the ITT population showed a similar trend (mPFS 8.4 vs 6.9 months, HR = 0.773, 95%CI 0.602-0.994). Descriptive analysis of OS showed a trend towards improved OS in the PD-L1 positive (mOS 32.8 vs 19.5 months; HR = 0.615, 95%CI 0.414-0.914) and the ITT population (mOS 33.1 vs 23.5 months; HR = 0.691, 95% CI 0.513-0.932). No new safety signals were identified. Grade >= 3 adverse events (AEs) (56.4% vs 54.3%) and fatal AEs (0.6% vs 3.4%) were similar between arms, while AEs leading to discontinuation of toripalimab/placebo (8.5% vs. 3.4%) and immune-related (irAEs) (40.8% vs. 24.0%) were more frequent in the toripalimab arm. Conclusions: The addition of toripalimab to nab-P provided a significant improvement in PFS for PD-L1 positive metastatic or recurrent TNBC patients receiving first-line treatment with an acceptable safety profile. Patients will be followed for the final PFS and OS analysis.