Discussion
toxicity
RECRUITMENT, VIRUS, DISEASE, RECRUITMENT, SECONDARY, TRANSFUSION REACTION, TRANSFUSION REACTIONS
In this paper we present the results of a randomized controlled phase I/IIa study (MULTIVIR-01) aiming at prevention or pre-emptive treatment of CMV/EBV viral reactivation in patients after aSCT. Patients received 3 consecutive doses of 21,000-41,000 CD3+ T cells per kg bodyweight and dose, separated by 2 intervals of at least 30 days. The primary endpoint of the study was to demonstrate safety of the T-cell product as assessed by the occurrence of an acute transfusion reaction and/or as late toxicity the development of acute GvHD. Both endpoints were met, as we did not observe any transfusion reactions in 25 T cell infusions, and the cumulative incidence of acute GvHD was not significantly different between the two groups. Thus, the product can be considered safe for application in humans.Several studies have aimed at prevention of reactivation predominantly for CMV employing various techniques of manufacturing including selection of specific T cells based on IFNγ production (To overcome the problem of early reactivation, several studies have employed partially HLA-matched third party CMV-, EBV-, or even multi-virus-specific T cells. In currently ongoing placebo controlled randomized phase III studies this concept is being explored in more than 60 centers worldwide (Clinicaltrials Identifier: NCT05305040) (The phase II part of this study suffered from low patient numbers in both groups, and we were not able to demonstrate any influence of the T cell product on any of the secondary endpoints monitored. Recruitment into the study was seriously compromised with the marketing authorization of letermovir as a prevention for CMV reactivation in late 2017. No preventative anti-viral treatment other than aciclovir was available when the study started recruiting in 2013. Although funding of letermovir was initially problematic and not secured in Germany, many care takers were reluctant to enroll patients into a phase I study when an approved drug for CMV prevention was available. Hence recruitment slowed down significantly over time and the study stopped recruiting in 2019.Patient 4, 5, 28 and 29 reactivated EBV as early as day 17, 20, 35 and 39 in the treatment group. These patients received the T-cell product on day 47, 51, 55, and 41, respectively, in a pre-emptive treatment fashion. In all four patients, EBV reactivation resolved within less than 10 days. Patients 4 and 28 were treated for EBV reactivation with 2 doses of rituximab. Our data neither confirm nor exclude a potential role of infused EBV-specific T cells in reversal of EBV reactivation in these patients. Only 2 of 4 patients within this group required treatment with rituximab as the copy numbers observed did not trigger treatment in 2 patients. Similarly, 2 patients of the control group were treated with rituximab; the difference between treatment and control groups was not statistically significant with regard to the use of rituximab. Patients 28 also reactivated CMV before receiving the first infusion of the T-cell product. Patients 4, 11 and 23 reactivated CMV after initiation of T-cell transfer. In contrast, 9 out of 14 patients in the control arm reactivated CMV beginning on day 30. Given this situation and the low number of patients in both groups, the study could not demonstrate prevention of reactivation of either virus. However, we noted a reduction of the cumulative incidence of CMV reactivation in the treatment group, which was significant when the observation period was limited to 100 days.The function of virus-specific T-cell transfer in prophylaxis and prevention of CMV reactivation or disease in stem cell recipients has been difficult to assess. Several studies have been published over the last two decades (The study was able to demonstrate expansion of T cells with specificity for CMV and EBV after the infusions in a number of cases. Patients 4, 5, 11, 23 and 28 displayed an increase in T cell numbers after infusion, especially when viral antigens were expected to be present due to reactivation. This is in our view an important finding, as it demonstrates activity of the T cells infused. It is noteworthy that the most substantial increase in T cells was seen in those patients where more than one of the required HLA class I loci was present. Especially presence of HLA B*07:02, B*08:01, and C*07:02 gave rise to a substantial expansion as shown for patient 4, 5, 11, and 28. In the presence of only HLA A*02:01 (patient 25) or in combination with HLA B*35:01 (patient 19) we were not able to demonstrate significant expansion, which is in contrast with our recent findings (In summary, we have been able to demonstrate that centralized manufacturing in an academic institution and application of virus specific T cells is feasible in a multi-center setup in spite of high logistical efforts. We have shown that the T-cell product can be safely applied and did not find any toxicity. The study fell short at demonstrating efficacy of the T-cell product mainly due low patient numbers but has provided the foundation for subsequent efficacy studies.