Administration of Most Closely HLA-Matched Multivirus-Specific T Cells for the Treatment of EBV, CMV, AdV, HHV6, and BKV Post Allogeneic Hematopoietic Stem Cell Transplant

Viral infections remain a significant cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Adoptive immunotherapy with donor-derived virus-specific T cells (VSTs) has proven safe and effective for the prophylaxis and treatment of EBV, CMV, AdV, BKV and HHV-6 infections post-HSCT. However, broader application is restricted by the time taken to prepare patient-specific products and the lack of virus-specific T cell precursors in cord blood and seronegative donors. Thus, to assess whether 3^rd party multivirus-directed VSTs could produce clinical benefit when administered as an “off the shelf” product to allogeneic HSCT recipients with refractory BKV, EBV, CMV, AdV and/or HHV-6 infections we initiated a Phase II clinical trial and now report interim results for 22 patients infused to date. We prepared a bank of 58 VST lines from individuals with common HLA polymorphisms by exposing donor PBMCs (3x10⁷) to overlapping peptide libraries spanning AdV (Hexon, Penton), EBV (LMP2, EBNA1, BZLF1), CMV (pp65, IE1), BKV (Large T, VP1) and HHV-6 (U11, U14, U90) antigens followed by a 9-11 day expansion phase in a G-Rex device in the presence of IL4 and IL7. This produced a mean of 4.2±1x10⁸VSTs that were polyclonal, comprising both CD4+ (61±2.4%) and CD8+ (34±2.1%) cells that expressed central (CD45RO+/CD62L+/CCR7+ - 43±3.9%) and effector memory markers (CD45RO+/CD62L- - 10±1%). 56/58 lines had activity against AdV, 50/58 against EBV, 35/58 against BKV, 34/58 against HHV-6, and 33/58 against CMV.  

To date, 62 HSCT recipients have been screened for study participation and a potential line, based on target virus specificity through a shared allele and overall HLA match, was identified for 58. Of these, 22 patients with infections that were unresponsive to at least 2 lines of antiviral treatment have been infused (fixed dose level - 2x10⁷ VSTs/m²) with VST lines matched at 1 to 6 HLA antigens. Seventeen received just 1 infusion, while 5 patients required 2 or more infusions for sustained benefit. Eight patients received VSTs for CMV infections, including 3 cases of CMV colitis, 8 for BKV (6 for cystitis, 2 for nephritis), 1 for HHV-6, 1 for EBV-PTLD, 1 for AdV, 1 for BKV and EBV, 1 for CMV and AdV and 1 for CMV and BKV infections. There were no immediate adverse effects related to infusion. Based on viral load measurements by quantitative PCR a single VST infusion successfully controlled active infections in 19/21 evaluable patients: CMV (4 CR, 5 PR, 1NR); EBV (2 CR); AdV (1 CR, 1 NR); BKV (1 CR, 7 PR); and HHV-6 (1 PR). Of note, all 6 patients with BK hemorrhagic cystitis and 2/3 patients with CMV colitis had marked improvement/resolution of symptoms following VST treatment. In 8 subjects who responded to VST therapy we saw an increase in virus-specific T cells post-infusion. These expanded cells were confirmed to be of 3^rd party VST origin in 3 patients and persisted for up to 6 weeks post-infusion. Finally, despite the HLA disparity of VSTs and recipients, de novo GvHD occurred in only one subject, who developed Grade I skin GVHD 1 week post-infusion, which resolved with the administration of topical steroids. One additional patient had a flare of chronic skin GVHD coincident with tapering of immunosuppression and 1 patient developed a transient fever 5 hours post-infusion, which spontaneously resolved. These results demonstrate the feasibility and safety of 3^rd party multivirus-directed VSTs, generated by direct stimulation of PBMCs with synthetic peptides and administered as an “off the shelf” product. The infused cells were capable of in vivo expansion in allogeneic HSCT recipients and proved clinically effective against refractory EBV, CMV and AdV infections and also controlled HHV-6 reactivation and BKV-associated hemorrhagic cystitis.