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Realgar-Indigo Naturalis Formula (RIF) is an oral form of arsenic that is effective against acute promyelocytic leukemia (APL). This multicenter, randomized, controlled trial compared the efficacy of all-trans retinoic acid (ATRA) plus RIF with ATRA plus arsenic trioxide (ATO) in a simplified regimen for non-high-risk APL. Following induction therapy with ATRA and ATO, participants were randomly assigned to receive either ATRA plus ATO or ATRA plus RIF both in a 2-week on 2-week off schedule for consolidation therapy. Once achieving molecular complete remission, the regimen was administered for a total of 6 cycles. All of 108 eligible patients achieved hematological complete remission after induction therapy. The median follow-up time was 29 months. The primary endpoint of two-year disease-free survival was 97% in the ATRA-RIF arm and 98% in the ATRA-ATO arm, respectively. (The ATRA-RIF arm was found to be non-inferior to the ATRA-ATO arm, (P < .01), with a percentage difference of -1% (95%CI, -4.8 to 6.9). No deaths have been observed. Most adverse events were moderate. This study confirms the noninferiority of RIF to ATO for non-high-risk APL, while also offering a more favorable regimen schedule for post-remission therapy. (ClinicalTrials gov. Identifier: as NCT02899169).

Antibody-drug conjugates (ADCs) represent one of the most successful therapeutic approaches introduced in clinical practice in the last few years. Loncastuximab tesirine (ADCT-402) is a CD19 targeting ADC, in which the antibody is conjugated through a protease cleavable dipeptide linker to a pyrrolobenzodiazepine (PBD) dimer warhead (SG3199). Based on the results of a phase 2 study, loncastuximab tesirine was recently approved for adult patients with relapsed/refractory large B-cell lymphoma. We assessed the activity of loncastuximab tesirine using in vitro and in vivo models of lymphomas, correlated its activity with CD19 expression levels, and identified combination partners providing synergy with loncastuximab tesirine. Loncastuximab tesirine was tested across 60 lymphoma cell lines. Loncastuximab tesirine had strong cytotoxic activity in B-cell lymphoma cell lines. The in vitro activity was correlated with CD19 expression level and intrinsic sensitivity of cell lines to the ADC’s warhead. Loncastuximab tesirine was more potent than other anti-CD19 ADCs (coltuximab ravtansine, huB4-DGN462), albeit the pattern of activity across cell lines was correlated. Loncastuximab tesirine activity was also largely correlated with cell line sensitivity to R-CHOP. Combinatorial in vitro and in vivo experiments identified the benefit of adding loncastuximab tesirine to other agents, especially BCL2 and PI3K inhibitors. Our data support the further development of loncastuximab tesirine as a single agent and in combination for patients affected by mature B-cell neoplasms. The results also highlight the importance of CD19 expression and the existence of lymphoma populations characterized by resistance to multiple therapies.

Hematopoietic stem cell transplantation following myeloablative chemotherapy is a curative treatment for many hematopoietic malignancies. However, profound granulocytopenia during the interval between transplantation and marrow recovery exposes recipients to risks of fatal infection, a significant source of transplant-associated morbidity and mortality. We have previously described the discovery of a small molecule, SW033291, that potently inhibits the prostaglandin degrading enzyme 15-PGDH, increases bone marrow prostaglandin E2, and accelerates hematopoietic recovery following murine transplant. Here we describe the efficacy of (+)-SW209415, a second-generation 15-PGDH inhibitor, in an expanded range of models relevant to human transplantation. (+)-SW209415 is 10,000-fold more soluble, providing the potential for intravenous delivery, while maintaining potency in inhibiting 15-PGDH, increasing in vivo prostaglandin E2, and accelerating hematopoietic regeneration following transplantation. In additional models, (+)-SW209415: (i) demonstrated synergy with granulocyte colony-stimulating factor, the current standard of care; (ii) maintained efficacy as transplant cell dose was escalated; (iii) maintained efficacy when transplant donors and recipients were aged; and (iv) potentiated homing in xenotransplants using human hematopoietic stem cells. (+)-SW209415 showed no adverse effects, no potentiation of in vivo growth of human myeloma and leukemia xenografts, and, on chronic high-dose administration, no toxicity as assessed by weight, blood counts and serum chemistry. These studies provide independent chemical confirmation of the activity of 15-PGDH inhibitors in potentiating hematopoietic recovery, extend the range of models in which inhibiting 15-PGDH demonstrates activity, allay concerns regarding potential for adverse effects from increasing prostaglandin E2, and thereby, advance 15-PGDH as a therapeutic target for potentiating hematopoietic stem cell transplantation.