An innovative strategy for solid tumors involves using bispecific T-cell engagers to target the tumor stroma—the protective fibrotic tissue surrounding the tumor. This novel approach aims to first eliminate this physical barrier, making the cancer cells themselves more vulnerable to subsequent immune attack.

A specific ALL subtype, PAX5-altered, often loses expression of the CD58 protein. CD58 is critical for creating a stable synapse between the T-cell and the cancer cell. Its absence leads to a "looser attachment," impairing the T-cell's ability to kill and thereby conferring resistance to immunotherapies like BiTEs and CAR-T.

Instead of focusing solely on T-cells, Create's platform first targets myeloid cells, which constitute up to 60% of some solid tumors. Programming these cells transforms the tumor microenvironment, enabling a 5-10x influx of CD8 T-cells. This overcomes a key barrier for T-cell therapies in solid tumors.

Genomic risk factors like TP53 mutations can predict immunotherapy failure mechanisms. In a case of TP53-mutated ALL, treatment with blinatumomab led to relapse with CD19-dim or negative disease. This suggests the underlying genomics predispose the cancer to shed its target antigen under therapeutic pressure.

Companies like VIR are making progress with masked T-cell engagers that limit systemic toxicity like cytokine release syndrome (CRS). This approach, which concentrates efficacy at the tumor site, could be the key to unlocking the broad potential of T-cell engagers beyond hematologic malignancies into the much larger solid tumor market.

To combat immunosuppressive "cold" tumors, new trispecific antibodies are emerging. Unlike standard T-cell engagers that only provide the primary CD3 activation signal, these drugs also deliver the crucial co-stimulatory signal (e.g., via CD28), ensuring full T-cell activation in microenvironments where this second signal is naturally absent.

The excitement around ICOS agonists for activating effector T-cells ignored a critical biological nuance: ICOS is also highly expressed on suppressive T-regulatory cells. Dr. Radvanyi notes this oversight led to therapies that inadvertently activated the very cells they aimed to overcome, a cautionary tale on scientific dogma.

Small cell lung cancer tumors are immunologically "cold" with few T-cells, limiting standard immunotherapy efficacy. Tarlatumab, a BiTE, physically links T-cells to tumor cells via the DLL-3 target, forcing an immune synapse and helping the immune system attack a tumor it would otherwise ignore.

A key failure pattern for blinatumomab is relapse in extramedullary sites (outside the bone marrow). An analysis found that 43% of relapses involved these sites, suggesting the therapy may not effectively reach or clear disease in areas like the CNS or lymph nodes, allowing blasts to hide and re-emerge.