IMA001 Is a Novel Therapeutic Molecule That Improves Hematological Parameters during Vaso-Occlusion in Sickle Cell Disease In Vivo

Introduction:

In sickle cell disease (SCD), the oxygenation/deoxygenation cycles contribute to hemoglobin S polymerization leading to red blood cell (RBC) sickling and alteration of their properties. Blood cell clusters build up in the circulation, obstruct blood capillaries and cause acute painful vaso-occlusive crises (VOCs), a hallmark of SCD. In a companion study, we have found that IMA001, a nucleotide involved in the synthesis of coenzymes central to cellular metabolism, markedly improved the critical hematological markers in SCD Townes mice. Here, using the same mouse model, we investigated the impact of IMA001 on hematological and vascular parameters after an acute episode of hypoxia/reoxygenation (H/R).

Experimental design:

IMA001 (185 mg/kg/day) or vehicle (phosphate-buffered saline) were administered intra-peritoneally for 36 days in Townes HbSS mice (n = 8 in each group). At the end of the treatment period, mice were subjected to acute H/R (8% oxygen for 3 hours and reoxygenation at room air for 1 hour) to evaluate the impact of IMA001 on safety, hematological and vaso-occlusive parameters. Blood was collected after H/R, followed by routine hematology counts, fetal hemoglobin (HbF) analysis and evaluation of total RBC reactive oxygen species (ROS) by flow cytometry. Plasma was collected to measure markers of intravascular hemolysis, endothelial activation [P-selectin (P-sel) and nitric oxide (NO)], and acute inflammation [serum amyloid P (SAP)]. Vascular congestion was evaluated on liver, lung, and kidney sections by immunohistochemistry using an RBC specific antibody and measured as % of field of view covered by RBCs.

Results:

Safety - Administration for 36 days of IMA001 was well tolerated, as no treatment-related deaths or abnormal clinical signs were reported during the treatment period and the H/R phase.

Markers of sickle anemia and intravascular hemolysis - IMA001 treatment improved anemia and hemolysis markers of HbSS mice subjected to H/R. As a matter of fact, after the H/R phase, mice treated with IMA001 showed higher hemoglobin levels (+1.3 g/dl, p<0.01) and RBC counts (+20%, p<0.05) compared to vehicle-treated mice, as well as lower numbers of circulating reticulocytes (-27%, p<0.0001), lower levels of plasma hemoglobin (-39%, p<0.001), plasma-free heme (-41%, p<0.0001), lactate dehydrogenase (-66%, p<0.0001), total bilirubin (-30%, p<0.0001) and indirect bilirubin (-30%, p<0.0001).

Fetal hemoglobin (HbF) expression in RBCs - IMA001-treatment resulted in a 1.7-fold increase in the number of circulating HbF-positive RBCs (F-cells) compared to controls (p<0.0001).

Oxydative stress in RBCs - Compared to vehicle-treated mice, RBCs of IMA001-treated mice showed a marked reduction in ROS levels (-33%, p<0.001).

Vascular congestion – Histological analysis of tissues from mice submitted to H/R revealed that IMA001 reduced vaso-occlusion. In comparison to vehicle, IMA001 significantly reduced vessel congestion in liver (-30%, p<0.01), lung (-35%, p<0.01) and kidney (-31%, p<0.0001) vessels.

Markers of endothelial activation, and inflammation - Soluble P-sel was moderately but significantly reduced in plasma from mice treated with IMA001 in comparison to the controls (-11%, p<0.05) with no differences found in the concentrations of neither SAP nor NO.

Conclusion:

Administration for 36 days of IMA001 to sickle Townes HbSS mice showed a potent protective effect during an acute episode of vaso-occlusion by reducing intravascular hemolysis and by inhibiting microvascular stasis and was well tolerated. Our study demonstrates the potential of IMA001 as a safe and effective molecule to improve hematological and vascular parameters during VOCs.