Autoimmune Cytopenias Following Alemtuzumab-Induced Renal Transplant: Clinical Features and Treatment Outcomes

Background: The anti-CD52 monoclonal antibody alemtuzumab (Alem) induces a rapid-onset, profound and long-lasting depletion of lymphocytes: B cells recover within 12 months, while T cell recovery is still incomplete after 30 months. Alem is used as induction therapy for solid organ transplantations, including renal. Autoimmune complications following Alem include thyroid disorders (20-30%), immune thrombocytopenia (ITP) (2-3%), and autoimmune hemolytic anemia (AIHA) and autoimmune nephropathies (< 1%).

Methods: we retrospectively analyzed 41 patients (pts) attending the Haematology Clinic at Hammersmith Hospital (HH), who developed autoimmune cytopenias (ITP or AIHA) after an Alem-induced renal transplant. The autoimmune cytopenia was defined as a rapid onset of isolated thrombocytopenia and/or anemia without other explanation.

For ITP, complete response (CR) and response (R) were defined according to IWG standard criteria (Rodeghiero,Blood,2009). For AIHA, CR was defined as a stable Hb level >120 g/L, no transfusion requirement and no signs of hemolysis; partial response (PR) as a rise in Hb levels >20 g/L, without transfusion requirement.

The study aim is to report clinical features and treatment outcomes of these 41 pts.

Results:

Between 1/11/05 and 14/12/16, 1431 pts received an Alem-induced renal transplant at HH. 34 (2.3%) developed ITP and 7 (0.48%) AIHA; 28 (68%) pts were males. Median age at renal transplant was 48 (range 20-69) years. The cytopenia developed a median of 35 months (range 6-161) after Alem administration. Median lowest platelet count was 5.5x10⁹/L (range 0-41) and median nadir of hemoglobin (Hb) was 58 g/L (range 35-65).

ITP pts: 2 pts achieved spontaneous CR. Of the remaining 32, 91% received steroids, IVIG or both as first line therapy, with an overall response rate (ORR) of 62%. 10 pts (31%) maintained the response without any further treatment. 22 pts required second line therapy, 11 required ≥ 3 lines of treatment. Treatments included: thrombopoietin receptor agonists (TPO-RA), rituximab (RTX), MMF and/or a combination.

TPO-RA were used 15 times, with an ORR of 80%, a relapse rate of 33% and a median duration of response (DOR) of 22 months (range 3-48); 10/12 pts (83%) who responded to TPO-RA, discontinued treatment after a median of 64 days (range 7 - 528): 6 maintained the response after discontinuation. RTX was used 10 times, with an ORR of 90%, a relapse rate of 22% and a median DOR of 27 months (range 3 - 83). A combination of RTX and TPO-RA was used 7 times, with an ORR of 71%, a relapse rate of 40% and a median duration of response (DOR) of 5 months (range 2-44); the 5 responders discontinued treatment after a median of 49 days (range 14-462): 3/5 maintained their response. After a median follow-up of 38 months (range 3-96), all ITP pts maintained a response (91% CR and 9% R); 4 were still on treatment (2 TPO-RA and 2 MMF).

AIHA pts: 6 of 7 (86%) pts with AIHA received first line steroids +/- IVIG with an ORR of 67%. 4 pts needed second line therapy: all received RTX with an ORR of 50%. 2 pts needed ≥ 3 lines of therapy. After a median follow-up of 68 months (range 27-102) all AIHA pts maintained a response (57% CR and 43% PR), without any ongoing treatment.

Adverse events: 33 pts (80%) experienced 1 or more adverse events (AEs): 25 cardiovascular (including 14 thrombosis), 21 infections (16 grade ≥3), 5 steroid-induced diabetes, 3 graft failures, 10 malignancies (6 solid tumors and 4 PTLD). 6 of the ITP pts also developed AIHA (Evans syndrome). 3 ITP pts died.

Conclusions: ITP and AIHA represent important complications of Alem-induced renal transplant. Response rates after first-line therapy for ITP were comparable to primary ITP (30%). However, long-term response rate, sustained response to RTX and the proportion of pts able to continue in remission after discontinuing TPO-RA are higher than seen with primary ITP. Recovery from cytopenias may occur in conjunction with T cell reconstitution post Alem (this is under investigation). The large majority of AEs were related to multifactorial heavy immunosuppression and increased thrombotic risk distinguishing this group of pts. Hence for ITP and AIHA, steroids should be limited, as they are curative in only a few pts and burdened by many side effects. Both RTX and a short course of TPO-RA appear valid options, but the choice should be driven by the individual balance between thrombotic and infectious risks versus persistence of cytopenias.