Vincristine-loaded platelets coated with anti-CD41 mAbs: a new macrophage targeting proposal for the treatment of immune thrombocytopenia.

Immune thrombocytopenia (ITP) is an autoimmune disorder in which platelet-reactive autoantibodies accelerate the destruction of platelets. Macrophages play an important role in ITP through Fc receptor (FcR)-mediated antigen presenting and platelet clearance. In this study, a novel drug delivery system of vincristine-loaded platelets coated with anti-CD41 mAbs (CD41-VCR-PLT, CD41-VLP) was successfully established. The therapeutic effects and safety of CD41-VLP in vitro and in vivo were evaluated, and the possible mechanism was also explored. The results showed that PLT-CD41 could load VCR with high drug loading (DL) and encapsulation efficiency (EE), which were up to 41.16 ± 1.92% and 60.73 ± 2.79%, respectively, where platelets had no obvious morphological or functional changes. CD41-VLP could facilitate vincristine accumulation in macrophages, where the intracellular VCR concentration was 30.72 ± 3.11% at 72 h, which was significantly increased compared with the other groups (P < 0.01), thus inhibiting macrophage cell viability and inducing apoptosis. The cell viability inhibition rate and total apoptosis rate were 73.06 ± 5.26% and 69.70 ± 4.26%, respectively, both much higher than those of the other groups (P < 0.05). In the ITP mouse model, CD41-VLP increased the platelet count in peripheral blood, which was 720 ± 197.98 × 109 L, and significantly improved the platelet count compared with that in the VCR group (P < 0.05); moreover, it reduced the systemic toxicity and peripheral neurotoxicity of vincristine. The possible mechanism was that CD41-VLP could precisely target M1 macrophages in spleen and liver tissues through FcγR, thus reducing the platelet destruction caused by M1 macrophages. Therefore, CD41-VLP provides a new targeted therapy for ITP treatment.