Immunological alterations after immunotherapy with short lived HBV‐TCR T cells associates with long‐term treatment response in HBV‐HCC

The application of hepatitis B virus (HBV)–T‐cell receptor (TCR) T‐cell immunotherapy in patients with HBV‐related hepatocellular carcinoma (HBV‐HCC) has been apathetic, as the expression of HBV antigens by both normal HBV‐infected hepatocytes and HCC cells with HBV‐DNA integration increases the risk of on‐target off‐tumor severe liver inflammatory events. To increase the safety of this immunotherapeutic approach, we developed messenger RNA (mRNA) HBV‐TCR‐redirected T cells that—due to the transient nature of mRNA—are functionally short lived and can be infused in escalating doses. The safety of this approach and its clinical potential against primary HBV‐HCC have never been analyzed in human trials; thus, we studied the clinical and immunological parameters of 8 patients with chronic HBV infection and diffuse nonoperable HBV‐HCC treated at weekly intervals with escalating doses (1 × 104, 1 × 105, 1 × 106, and 5 × 106 TCR+ T cells/kg body weight) of T cells modified with HBV‐TCR encoding mRNA. The treatment was well tolerated with no severe systemic inflammatory events, cytokine storm, or neurotoxicity observed in any of these patients throughout treatment. Instead, we observed a destruction of the tumor lesion or a prolonged stable disease in 3 of 8 patients. Importantly, the patients without clinically relevant reductions of HCC did not display any detectable peripheral blood immunological alterations. In contrast, signs of transient localized liver inflammation, activation of the T‐cell compartment, and/or elevations of serum chemokine (C‐X‐C motif) ligand (CXCL) 9 and CXCL10 levels were detected in patients with long‐term clinical benefit. Conclusion: We show that despite the reduced in vivo half‐life (3‐4 days), adoptive transfer of mRNA HBV‐TCR T cells into patients with HBV‐HCC show long‐term clinical benefit that was associated with transient immunological alterations.