Impact of CMV-specific immune reconstitution at the end of letermovir prophylaxis on the development of late cytomegalovirus infection in haematopoietic stem cell transplant recipients (INMUNOEND): a protocol for a prospective, observational, multicentre study.

Introduction: Cytomegalovirus (CMV) infection is a common complication in patients undergoing haematopoietic stem cell transplantation (SCT). Letermovir (LTV) prophylaxis during the first 100 days post-SCT is effective and safe in preventing this infection, although it may be associated with a delay in CMV-specific immune reconstitution. Hence, a study is needed to evaluate whether the absence of CMV-specific immune reconstitution at the end of LTV prophylaxis is associated with the development of late infection. This could facilitate the individualisation of CMV prophylaxis duration in these patients.

Methods and analysis: INMUNOEND is a multicentre, prospective, observational, non-interventional study including CMV seropositive patients undergoing allo-SCT who receive LTV prophylaxis during the first 100 days post SCT. Immunological and virological monitoring will be conducted until day+200 post-SCT. The primary outcome is the percentage of patients who develop clinically significant CMV infection up to day+200 post-SCT after completing LTV prophylaxis. Data collected will include baseline characteristics of the haematological diseases and comorbidities, variables related to SCT (ie, engrafment, graft-versus-host disease, use of LTV and CMV replication) and variables related to CMV-specific immune reconstitution.

Ethics and dissemination: Ethical approval has been obtained from the institutional review board (Comité de Ética de la Investigación de Córdoba; SICEIA-2024-0 01 762). The results of this study will be published in peer-reviewed journals and disseminated at national and international conferences.

Trial registration number: NCT06814301.