Unlike some targeted therapies that lead to antigen loss, treatment with the CD19-directed antibody tafasitamab does not appear to eliminate CD19 expression on lymphoma cells. This is a critical finding, as it preserves the target for subsequent potent therapies like CD19-directed CAR T-cells.

To maximize the effectiveness of CD19-directed CAR-T therapy (Lysocel) in CLL, patients should be referred while still responding to their latest line of salvage therapy, such as pirtobrutinib. This approach leverages less-exhausted T-cells and real-world data shows it leads to higher complete remission rates.

Clinicians should not be deterred from using CD19 CAR T-cell therapy in patients who have previously received other CD19-targeting agents like tafasitamab. Preclinical and retrospective clinical data suggest prior exposure does not impair CAR T efficacy, and therefore re-testing for CD19 expression is unnecessary.

The argument against using certain frontline therapies for fear of compromising future CAR-T eligibility is tempered by a stark reality: only 5% of eligible US patients actually receive CAR-T. This logistical and access bottleneck means that optimizing immediate, available treatments is paramount for the vast majority of patients.

Using a BCMA bispecific antibody first can exhaust a patient's T-cells or cause tumors to lose the BCMA target, rendering a subsequent BCMA-targeted CAR-T therapy ineffective. The optimal sequence is CAR-T first, which preserves T-cell function and BCMA expression, leaving bispecifics as a viable later-line option.

A key clinical concern with CD19-directed therapies is antigen loss, which could prevent future CAR T-cell treatments. Data from the INMIND trial alleviates this fear, showing that 23 of 24 post-treatment lymphoma samples retained CD19 expression, suggesting tofacitimab does not preclude subsequent CAR-T therapy.

In the IN-MIND trial for relapsed follicular lymphoma, the tafasitamab-lenalidomide-rituximab arm had zero cases of histologic transformation to a more aggressive lymphoma. This contrasts with nine cases in the control arm, suggesting the CD19-targeting antibody may eradicate precursor cells responsible for this dreaded complication.

The first successful CAR T-cells targeted CD19, a protein on leukemia cells but also on healthy B-cells. The therapy worked because humans can live without B-cells. This "tolerable collateral damage" was serendipitous and highlights the primary challenge for other cancers: finding targets that won't cause fatal damage to healthy organs.

Before initiating a CD20-targeting bispecific antibody in patients who have failed CAR-T therapy, a new biopsy is mandatory. Up to 30% of these patients experience CD20 antigen loss, which would render the bispecific therapy ineffective and necessitates choosing a drug with a different target.