Production and nonclinical evaluation of an autologous iPSC–derived platelet product for the iPLAT1 clinical trial

Abstract

Donor-derived platelets are provided to treat or prevent hemorrhage in patients with thrombocytopenia. However, approximately 5% or more of these patients are complicated with alloimmune platelet transfusion refractoriness (allo-PTR) due to alloantibodies against class I human leukocyte antigens (HLA-I) or human platelet antigens (HPA). In these cases, platelets from compatible donors are necessary, but it is difficult to find such donors for patients with rare HLA-I or HPA. Aiming to produce platelet products for an aplastic anemia patient with allo-PTR due to rare HPA-1 mismatch in Japan, we have developed an ex vivo good manufacturing process (GMP)-based production system for an induced pluripotent stem cell-derived platelet product (iPSC-PLTs). Immortalized megakaryocyte progenitor cell lines (imMKCLs) were established from patient iPSCs, and a competent clone was selected for the master cell bank (MCB) and confirmed for safety including negativity of pathogens. From this MCB, iPSC-PLTs were produced using turbulent flow bioreactors and new drugs. In extensive non-clinical studies, iPSC-PLTs were confirmed for quality, safety, and efficacy, including hemostasis in a rabbit model. This report displays a complete system for the GMP-based production of iPSC-PLTs and the required non-clinical studies, and thus supports the iPLAT1 study, the first-in-human clinical trial of iPSC-PLTs, in a patient with allo-PTR and no compatible donor using the autologous product. It also serves as a comprehensive reference for the development of widely applicable allogeneic iPSC-PLTs and other cell products which use iPSC-derived progenitor cells as an MCB.

Ex Vivo Production of Platelets From iPSCs: The iPLAT1 Study and Beyond

“…Another possibility is that, unlike the 1-hour peak for donor-derived platelets, iPSC-PLTs may have peaked later at 2-6 hours posttransfusion as evidenced by some animal circulation studies. 16,17 On the contrary, a slight increase in a coagulation marker, d-dimer, was observed after transfusion in the third cohort, 16 raising the possibility that unexpected coagulation of iPSC-PLTs had occurred soon after transfusion. The potential causes of this suspected compromise in iPSC-PLT circulation will be discussed in the sections below.…”

“…This seamless closed‐system process is followed by packaging in a blood bag with approximately 10 × 10 11 iPSC‐PLTs in 200 mL bicarbonated Ringer's solution with 20% acid citrate dextrose and 2.5% human serum albumin 33 . Finally, the bag is irradiated with 25 Gy to eliminate the tumorigenicity of any remaining nucleated cells 17 . The DOX‐OFF maturation‐to‐packaging process mentioned here delicately handles the generated iPSC‐PLTs.…”

“…To ensure the safety of iPSC‐PLTs, comprehensive nonclinical studies have been conducted 17 . First, it is a prerequisite that the production system to be based on GMP standards.…”

“…15 As for blood products, the clinical trial of autologous iPSC-derived platelet products (iPSC-PLTs), iPLAT1, was conducted from 2019 to 2022. 16,17 The clinical application of iPSC-derived red blood cell (RBC) products requires more time because of several obstacles. [18][19][20][21] For instance, a much greater number of RBCs is needed for standard transfusion than platelets, whereas 1 erythroblast can produce only 1 RBC through enucleation.…”

Genetically engineered transfusable platelets using mRNA lipid nanoparticles

“…Circulating platelets can be permanently modified through a bone marrow transplant of genetically modified megakaryocytes, for example, to correct hemophilia A (6)(7)(8). Platelet-like particles can be cultured from stem cells, which produce low quantities of cells that have been transfused into people (9,10). In contrast, authentic platelets collected from blood donors and intended for transfusion are available in large quantities and retain important functions of circulating platelets (11).…”