Anti-CD45 radioimmunotherapy without TBI before transplantation facilitates persistent haploidentical donor engraftment

Abstract

Many patients with hematologic malignancies cannot tolerate hematopoietic cell transplantation (HCT), whereas others may not have a compatible human leukocyte antigen-matched donor. To overcome these limitations, we optimized a conditioning regimen employing anti-CD45 radioimmunotherapy (RIT) replacing total body irradiation (TBI) before haploidentical HCT in a murine model. Mice received 200 to 400 μCi (90)Y-anti-CD45 antibody (30F11), with or without fludarabine (5 days starting day -8), with cyclophosphamide (CY; days -2 and +2) for graft-versus-host disease prophylaxis, and 1.5 × 10(7) haploidentical donor bone marrow cells (day 0). Haploidentical bone marrow transplantation (BMT) with 300 μCi (90)Y-anti-CD45 RIT and CY, without TBI or fludarabine, led to mixed chimeras with 81.3 ± 10.6% mean donor origin CD8(+) cells detected 1 month after BMT, and remained stable (85.5 ± 11% mean donor origin CD8(+) cells) 6 months after haploidentical BMT. High chimerism levels were induced across multiple hematopoietic lineages 28 days after haploidentical BMT with 69.3 ± 14.1%, 75.6 ± 20.2%, and 88.5 ± 11.8% CD3(+) T cells, B220(+) B cells, and CD11b(+) myeloid cells, respectively. Fifty percent of SJL leukemia-bearing mice treated with 400 μCi (90)Y-DOTA-30F11, CY, and haploidentical BMT were cured and lived >200 days. Mice treated with 200 μCi (90)Y-DOTA-30F11 had a median overall survival of 73 days, while untreated leukemic mice had a median overall survival of 34 days (P < .001, Mantel-Cox test). RIT-mediated haploidentical BMT without TBI may increase treatment options for aggressive hematologic malignancies.

Figure 1

Chimerism following haploidentical BMT with a conditioning regimen of ⁹⁰Y-anti-CD45 RIT and FLU. (A) Mean CD8⁺ donor chimerism in peripheral blood 28 days after haploidentical BMT in mice given FLU × 5 days (100 mg/kg per day IP on days −8 to −4) and 200, 300, or 400 µCi ⁹⁰Y-DOTA-30F11 on day −3 followed by 1.5 × 10⁷ haploidentical BM cells on day 0. (B) MFC analysis of peripheral blood 28 days after haploidentical BMT in a B6SJLF1/J transplanted mouse pretreated with FLU 100 mg/kg per day × 5 days and 200 µCi ⁹⁰Y-DOTA-30F11, depicting the percentage of CD8⁺ cells expressing the H-2D^d haplotype.

Figure 2

Chimerism following haploidentical BMT with a conditioning regimen of ⁹⁰Y-anti-CD45 RIT without FLU. (A) Mean CD8⁺ donor chimerism in peripheral blood 28 days after haploidentical BMT in mice pretreated with 200, 300, or 400 µCi ⁹⁰Y-DOTA-30F11 on day −3, without FLU. MFC analysis of peripheral blood 28 days after haploidentical BMT in a B6SJLF1/J mouse pretreated with (B) FLU × 5 days (100 mg/kg per day IP on days −8 to −4) and 400 µCi ⁹⁰Y-DOTA-30F11 on day −3 or (C) FLU × 5 days without anti-CD45 RIT, both transplanted with 1.5 × 10⁷ haploidentical BM cells on day 0, depicting the percentage of CD8⁺ cells expressing the H-2D^d haplotype.

Figure 3

Chimerism following haploidentical BMT with a conditioning regimen of ⁹⁰Y-anti-CD45 RIT with pre- and post-BMT CY. MFC analysis of peripheral blood 28 days after haploidentical BMT in a B6SJLF1/J transplanted mouse that received 1.5 × 10⁷ haploidentical BM cells on day 0 and (A) 300 µCi ⁹⁰Y-DOTA-30F11 on day −3 and CY (200 mg/kg per day on days −2 and +2) or (B) CY alone without RIT, depicting the percentage of CD8⁺ cells expressing the H-2D^d haplotype.

Figure 4

Chimerism following haploidentical BMT with a conditioning regimen of ⁹⁰Y-anti-CD45 RIT, FLU, and/or CY. Mean percentage of CD8⁺ cells expressing the H-2D^d haplotype in peripheral blood from transplanted mice 28 days after BMT. Recipient mice were treated with 300 µCi ⁹⁰Y-DOTA-30F11 on day −3 alone, with FLU × 5 days (100 mg/kg per day on days −8 to −4), with CY (200 mg/kg per day on days −2 and +2), or with both FLU and CY.

Figure 5

Overall survival using ⁹⁰Y-anti-CD45 RIT and haploidentical BMT in leukemia-bearing mice. Survival of SJL leukemia-bearing mice treated with pre- and posttransplant CY (200 mg/kg per day on days −2 and +2), (black box) 200 or (black inverse triangle) 400 µCi of ⁹⁰Y-DOTA-30F11, or (gray diamond) 400 µCi ⁹⁰Y-DOTA-rat IgG on day −3 or −4, and transplanted on day 0 with 1.5 × 10⁷ haploidentical BM cells. Untreated leukemia-bearing mice (gray circle) served as controls.

Figure 6

Multilineage chimerism following haploidentical BMT with a conditioning regimen of ⁹⁰Y-anti-CD45 RIT, TBI, and/or CY. Individual and mean percentages of (A) CD3⁺ (T cells), (B) B220⁺ (B cells), or (C) CD11b⁺ (myeloid cells) expressing the H-2D^d haplotype in peripheral blood from transplanted mice 28 days after BMT. Recipient mice were treated with 100 or 300 µCi ⁹⁰Y-DOTA-30F11 on day −4 or 200 or 1000 cGy TBI on day 0 and with CY (200 mg/kg per day on days −2 and +2).