Nongenotoxic antibody-drug conjugate conditioning enables safe and effective platelet gene therapy of hemophilia A mice

Chunyan Gao, Jocelyn A. Schroeder, Feng Xue, Weiqing Jing, Yuanhua Cai, Amelia Scheck, Saravanan Subramaniam, Sridhar Rao, Hartmut Weiler, Agnieszka Czechowicz*, Qizhen Shi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Gene therapy offers the potential to cure hemophilia A (HA). We have shown that hematopoietic stem cell (HSC)–based platelet-specific factor VIII (FVIII) (2bF8) gene therapy can produce therapeutic protein and induce antigen-specific immune tolerance in HA mice, even in the presence of inhibitory antibodies. For HSC-based gene therapy, traditional preconditioning using cytotoxic chemotherapy or total body irradiation (TBI) has been required. The potential toxicity associated with TBI or chemotherapy is a deterrent that may prevent patients with HA, a nonmalignant disease, from agreeing to such a protocol. Here, we describe targeted nongenotoxic preconditioning for 2bF8 gene therapy utilizing a hematopoietic cell–specific antibody-drug conjugate (ADC), which consists of saporin conjugated to CD45.2- and CD117-targeting antibodies. We found that a combination of CD45.2- and CD117-targeting ADC preconditioning was effective for engrafting 2bF8-transduced HSCs and was favorable for platelet lineage reconstitution. Two thirds of HA mice that received 2bF8 lentivirus-transduced HSCs under (CD45.21CD117)-targeting ADC conditioning maintained sustained therapeutic levels of platelet FVIII expression. When CD8-targeting ADC was supplemented, chimerism and platelet FVIII expression were significantly increased, with long-term sustained platelet FVIII expression in all primary and secondary recipients. Importantly, immune tolerance was induced and hemostasis was restored in a tail-bleeding test, and joint bleeding also was effectively prevented in a needle-induced knee joint injury model in HA mice after 2bF8 gene therapy. In summary, we show for the first time efficient engraftment of gene-modified HSCs without genotoxic conditioning. The combined cocktail ADC-mediated hematopoietic cell–targeted nongenotoxic preconditioning that we developed is highly effective and favorable for platelet-specific gene therapy in HA mice.

Original languageEnglish (US)
Pages (from-to)2700-2711
Number of pages12
JournalBlood Advances
Issue number18
StatePublished - Sep 24 2019

ASJC Scopus subject areas

  • Hematology


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