Of 271 patients who received mogamulizumab in the 3 clinical trials, 32 patients underwent allo-HSCT after mogamulizumab treatment between 2013 and 2017 (CTCL, n = 23; ATL, n = 7; PTCL, n = 2), and their baseline characteristics are presented in Table 1. Twenty-two patients were identified in the United States, 3 in the United Kingdom, 2 each in France and Spain, and 1 each in Japan, the Netherlands, and Switzerland.

Among the 23 patients with CTCL, 13 (57%) had a diagnosis of MF, and 10 (43%) had a diagnosis of SS. Thirteen patients (57%) with CTCL were stage IVA at study entry, 1 of whom had transformed MF with primary stage IV disease. The mean (SD) number of mogamulizumab infusions was 11.3 (10.8) in patients with MF (median [range] 9 [2, 43]) and 15.8 (16.2) in patients with SS (median [range] 8 [3, 49]). Among patients with ATL, 3 patients (43%) each had lymphomatous or acute disease, and 1 patient had chronic disease. Four patients (57%) with ATL were stage IV at study entry, 1 patient was stage II, and 2 patients did not have reported stages. Two patients with PTCL were included in this study, one of whom had stage III disease at study entry and the other of whom had stage IV disease.

Human leukocyte antigen (HLA) matching was based on peripheral blood for 21 of the 32 patients (66%), bone marrow for 6 patients (19%), and was unknown for 5 patients (16%) (Fig. 1a). HLA-matched donors were related for 17 patients (53%) and unrelated for 11 patients (34%); relationship status was unknown for 4 patients (13%) (Fig. 1b). The most common conditioning regimens used in this patient population were fludarabine (21 patients [66%]), busulfan (11 patients [34%]), and melphalan (9 patients [28%]) (Fig. 2a). Among the 21 patients treated with fludarabine, 12 (57.1%) were also treated with busulfan and 6 (28.6%) were also treated with melphalan (Fig. 2b). The most common GVHD prophylaxis agents used in this patient population were tacrolimus (19 patients [59%]), methotrexate (12 patients [38%]), and cyclosporine (9 patients [28%]) (Fig. 3a). Ten (52.6%) of the patients treated with tacrolimus were also treated with methotrexate and 5 (26.3%) were also treated with mycophenolate mofetil (Fig. 3b).

a Allo-HSCT donor transplant source and (b) donor type. ATL adult T-cell leukemia/lymphoma, CTCL cutaneous T-cell lymphoma, HSCT hematopoietic stem cell transplantation, MF mycosis fungoides, PTCL peripheral T-cell lymphoma, SS Sézary syndrome. aIncludes one patient with transformed MF

a Agents used in conditioning regimensa. b Selected conditioning regimen combinations. ATG antithymocyte globulin, ATL adult T-cell lymphoma, CTCL cutaneous T-cell lymphoma, ICE ifosfamide, carboplatin, etoposide, MF mycosis fungoides, PTCL peripheral T-cell lymphoma, TBI total body irradiation, TLI total lymphoid irradiation, TSEBT total skin electron beam therapy. aReported agents based on retrospective chart review. Some are known not to be utilized for conditioning (eg, ICE, cyclosporine); some agents may be used in combination. bIncludes one patient with transformed MF

a Agents used in the GVHD prophylaxis and/or treatment of GVHDa. b Selected combination regimens for GVHD prophylaxis and/or Treatment. ATG antithymocyte globulin, ATL adult T-cell lymphoma, CTCL cutaneous T-cell lymphoma, MF mycosis fungoides, PTCL peripheral T-cell lymphoma. aReported agents based on retrospective chart review; some are not known to be utilized for prophylaxis (e.g., F 652, penicillin V potassium, prednisolone, ruxolitinib, sulfamethoxazole and trimethoprim, and valacyclovir). bIncludes one patient with transformed MF

Overall, 22 patients (69%) experienced GVHD, 8 patients (25%) reported no GVHD, and GVHD status was unknown for 2 patients (Supplemental Fig. 1A). Among those patients who experienced GVHD, 6 patients (27%) had grade 3 GVHD, and 2 patients (9%) had grade 4 (Supplemental Fig. 1B). Detailed information on the 8 patients with severe GVHD is provided in Supplementary Table 1. Both instances of grade 4 GVHD involved the intestinal tract, and 1 of these instances was reported to be steroid refractory. In those patients with grade 3–4 GVHD, 4 patients (50%) had related donors and 4 patients (50%) had unrelated donors. GVHD was reported as acute/hyperacute in 13 instances and chronic in 5 patients (including some patients with both) and was not described in 9 instances. Acute versus chronic status was known for only 11 instances in CTCL, 4 instances in ATL, and 2 instances in PTCL, with most instances being grade 1 acute GVHD. One instance of grade 3 hyperacute GVHD involving the skin along with grade 2 GVHD of the gut was reported in a patient with stage IV PTCL. This patient had undergone allogeneic transplant 44 days after their last mogamulizumab infusion and had conditioning with thiotepa, fludarabine, and busulfan. Tacrolimus and rapamycin were used for GVHD prophylaxis.

Patients with CTCL experienced 3 instances of grade 3–4 acute GVHD and no instances of grade 3–4 chronic GVHD. When MF and SS were examined separately, there were 8 patients (61.5%) with MF with GVHD of any grade (3 [20.0%] with grade 3–4 GVHD) and 8 patients (80%) with SS with GVHD (2 [20.0%]) with grade 3–4 GVHD). Patients with ATL experienced 1 instance of grade 3–4 chronic GVHD and no instances of grade 3–4 acute GVHD. One patient with PTCL experienced grade 3–4 acute GVHD, and no other grade 3–4 GVHD was reported. Seven patients (31.8%) who experienced GVHD had fludarabine + busulfan for conditioning and tacrolimus + methotrexate for GVHD prophylaxis.

Among all patients with known GVHD, mean (SD) time from last mogamulizumab infusion to transplant was 281.3 (191.7) days (median [range], 233.0 [16.0, 677.0] days). In patients with MF who experienced GVHD, the mean time was 269.6 (150.5) days (median [range], 265.0 [54, 509]), compared with 301.7 (224.5) days (219.0 [16.0, 677.0]) for patients with SS. Mean (SD) time since last mogamulizumab infusion in patients with no grade 1–2, or grade 3–4 GVHD, was 380.4 (227.3), 280.3 (173.8), and 261.3 (221.0), respectively (median [range] 297.5 [133, 805], 293.5 [16, 642], and 195 [44, 677], respectively). Two patients with known GVHD underwent transplant < 50 days after their last dose of mogamulizumab. One patient with CTCL underwent transplant 16 days after mogamulizumab and experienced GVHD of grade 2 in the skin and grade 1 in the skin, abdomen, colon, and eye. One patient with PTCL underwent transplant 44 days after mogamulizumab and experienced GVHD of grade 3 in the skin and grade 2 in the gut (described in detail above). Of 19 patients who underwent transplant between 50 and 365 days after their last dose of mogamulizumab, GVHD occurred in 14 of them, 5 of whom had grade 3–4 GVHD. Six patients who underwent transplant over 365 days after their last dose of mogamulizumab also experienced GVHD. Additional information on time since last mogamulizumab infusion is shown in Fig. 4.

Time since last mogamulizumab infusion

At last follow-up, 22 patients (69%) were still alive (median [range] follow-up, 998.0 days [131.0, 1592.0]), and 9 patients had died. Deceased patients had a median (range) survival time at last follow-up of 290.0 days (15.0, 761.0).