Efficacy of the antiCD38 Monoclonal Antibody Isatuximab in the Treatment of PCRA by Major ABO Mismatch After Allogeneic Hematopoietic Stem Cell Transplantation

A quarter of allogeneic hematopoietic stem cell transplantation are performed in a situation of major ABO mismatch exposing patients to the risk of immunological pure red cell aplasia (PRCA) after transplant. PCRA after transplant is defined as anemia with low reticulocytes count (under 10 G/L) after day 60 despite good leucocytes and platelet engraftment, full donor chimerism, associated with the persistence of recipients hemagglutinins (anti-A or anti-B antibodies). Bone marrow evaluation when performed show erythroid hypoplasia. Red blood cells transfusions are necessary every two weeks until remission leading to impaired quality of life (anemia, repeated hospitalization), iron overload, and need for iron chelation therapy. Treatments currently used are inefficient (anti CD20 monoclonal antibodies, EPO, steroids, plasma exchanges, proteasome inhibitors) or at risk of severe acute GVHD (donor lymphocytes infusion). PRCA has been demonstrated to be associated with the persistence of recipient's plasma cells.

Anti-CD38 monoclonal antibodies which targets plasma cells secreting hemagglutinins responsible of PCRA are a promising treatment: 6 cases reported in the literature support a rapid and sustain efficacy but a prospective randomized evaluation of its efficacy and safety in this context is necessary.

The main objective of the study is to assess the efficacy of the treatment of PRCA by isatuximab after allogeneic hematopoietic stem cell transplant compared to supportive care only control group (reduction in PRCA resolution time in days)


Eligibility Criteria:
Inclusion Criteria:

* Aged 15 years or older
* Having receiving an allogeneic hematopoietic stem cell transplantation in condition of major ABO mismatch
* PCRA defined by persistent red blood cell transfusion dependence at day 60 post-transplant with reticulocytes count under 10 G/L despite full donor chimerism and a good leucocytes (\>1 G/L) and platelet (\>50G/L) recovery
* No relapse or progression of underlying disease
* Contraception methods must be prescribed during all the duration of the research and using effective contraceptive methods during treatment for women of childbearing age (continue abstinence from heterosexual intercourse is accepted) and for man during the study treatment period and for at least 5 months after the last dose of study treatment and refrain from donating sperm during this period
* With health insurance coverage
* Having signed a written informed consent (2 parents for patients aged less than 18)

Exclusion Criteria:

* Aged \< 15 years
* Relapse of underlying disease
* Leucocyte chimerism \< 95%
* PRCA related to Parvovirus B19 infection (positive blood PCR)
* Known to be HIV+ or to have hepatitis A, B, or C active infection
* Active tuberculosis
* Pregnancy (βHCG positive) or breast-feeding.
* Patient receiving recombinant human erythropoietin.
* Patient receiving proteasome inhibitor (Bortezomib for example).
* Patient receiving thrombopoietin receptor agonists (ARTPO).
* Patient receiving plasma or plasmapheresis exchanges after transplant.
* Planned to receive any investigational drug within 14 days or 5 half-lives of the investigational drug, whichever is longer.
* Any clinically significant, uncontrolled medical conditions that, in the Investigator's opinion, would expose excessive risk to the patient or may interfere with compliance or interpretation of the study results.
* Hypersensitivity to the active substance or history of intolerance to steroids, mannitol, pregelatinized starch, sodium stearyl fumarate, histidine (as base and hydrochloride salt), arginine, hydrochloride, poloxamer 188, sucrose or any of the other components of study therapy that are not amenable to premedication with steroids and H2 blockers or would prohibit further treatment with these agents.
* Who have any debilitating medical or psychiatric illness
* Under tutorship or curatorship
* Who not understand informed consent for an optimal treatment and follow-up