e19011
Background: Chimeric Antigen Receptor T-cell (CAR-T) therapy can induce durable remission in some patients but requires time for a patient’s own cells to be reengineered to produce CAR proteins that can bind to and destroy cancer cells. During this time, bridging therapy is often used in debulking to reduce treatment toxicities and to control the disease while waiting for the manufacturing of CAR-T cells. Because bridging therapy often involves systemic treatment, the bridging therapies can induce responses, in and of themselves, in clinical trials testing CAR-T therapies. As such, we sought to assess bridging therapies used in CAR-T trials. Methods: Using the FDA labels (labels.fda.gov) to identify the indications and the pivotal clinical trials that led to the approval of each CAR-T cell therapy, we looked at which bridging therapies were used, whether multiple therapies were combined, response rates, and the reported adverse events associated with bridging therapy. We took note of all relevant comments regarding bridging therapy in the main paper and supplemental results. Results: Of the 11 studies testing CAR-T therapies, 10 reported the bridging therapies that were used in the study. Notably, only three of 11 studies provided clear information about which combinations of bridging therapy treatments were used during the trials. Of those that reported the types of bridging therapies (n=10), the most commonly used bridging therapy was dexamethasone, which was used in every study (10/10). The next three most commonly used treatments include rituximab (6/10), gemcitabine (5/10), and etoposide (5/10). Of the trials, 2/11 clearly reported whether patients had a complete response (CR), partial response (PR), or very good partial response (VGPR) to bridging therapy. 5/11 vaguely reported responses, using terminology outside of CR, PR, VGPR. 4/11 trials did not report or mention any response information in regards to bridging therapy. Of all the trials, 1/11 clearly reported adverse events associated with bridging therapy in the supplement, while 10/11 of the trials listed adverse events associated with the treatment groups, without clarifying those associated with bridging. Conclusions: Although patients are often refractory to first-line therapies, which share considerable overlap with the bridging therapies used, these therapies may still induce responses. Despite this possibility, the reporting of bridging therapy combinations and their subsequent response rates and adverse event rates, is highly variable. Of 11 pivotal clinical trials that led to the approval of a CAR-T cell therapy, none clearly reported bridging therapy data that encompassed all three categories (combinations used, response rates, adverse events). What is more, these data were often omitted completely. These findings highlight the need for greater transparency in the reporting of bridging therapy in order to more reliably assess the efficacy of CAR-T therapies.
