Rational Design for persistence

In this episode, we examine the work of Roselli et al.1, who explore a critical frontier in CAR T cell engineering: how to build T cells that don’t just kill tumors effectively, but also survive, persist, and adapt in the complex and hostile environments characteristic of solid tumors and relapsing hematologic malignancies.Building on themes from earlier episodes—such as the impact of co-stimulatory domains (CD28 vs. 4-1BB), strategies to reduce tonic signaling (Eyquem et al.), and optimizing cytokine support (IL-15)—this paper asks: Can we combine the best aspects of multiple co-stimulatory signals into a single CAR design? And, can dual-antigen targeting reduce the likelihood of tumor escape?Roselli et al. engineer several new CARs that incorporate both 4-1BB (for metabolic fitness and longevity) and a modified version of CD28 (mut06) designed to reduce exhaustion while retaining strong activation. They also explore tandem CARs targeting both CD19 and CD20, to limit the risk of antigen escape—a known challenge with CD19-directed therapies.Using the xCelligence platform, in vivo models, and transcriptional profiling, they show that these dual co-stimulatory CARs outperform their single-signal counterparts in terms of cytotoxicity, expansion, cytokine production, and resistance to exhaustion. The final experiments confirm that dual-antigen targeting not only delays relapse but also increases T cell persistence and flexibility, especially in tumors with heterogeneous antigen expression.In the broader arc of this podcast, this paper illustrates the field’s move toward rational CAR design and continuous improvement—combining lessons from receptor architecture, signaling dynamics, immune memory, and tumor evolution to create therapies that are both powerful and durable.