A Multi-Lineage Oral Hemokine™ HQK-1002 Enhances Neutrophil Recovery in Sub-Lethally Irradiated Mice and in Baboons.

Abstract 2509

Poster Board II-486

Acute radiation syndrome and therapeutic radiation are associated with cytopenias, notably severe neutropenia, particularly when large regions of bone marrow are exposed. An orally-active neutrophil stimulant which reduces the duration or magnitude of neutropenia would offer therapeutic benefit in radiation therapy and would be useful for acute radiation exposure. Orally-bioavailable short-chain fatty acid derivatives (SCFAD, Hemokines^TM HQK-1002 and its S-enantiomer HQK-1002S), which stimulate proliferation of growth factor-dependent hematopoietic cell lines and CFU-GM cultures, were evaluated for in vivo activity in irradiated and 5-FU-treated mice and in normal baboons. In sub-lethal irradiation studies, mice were irradiated (6 Gy single dose) and then treated with saline or HQK-1002 once daily, 5 days/week for 2 weeks, beginning on day 1 after irradiation, and absolute neutrophil counts (ANC) were determined. The mean nadir of absolute neutrophil counts (ANC) <500/mm³ was 6 days in sub-lethally-irradiated mice treated with HQK-1002, and 18 days in the saline treated controls. In HQK-1002 treated mice, ANC did not decline below 200/mm³, while saline-treated animals experienced 10 days of severe neutropenia with ANC <200/mm³. In lethally-irradiated (LD₉₀) mice, either saline or the (S) enantiomer of HQK-1002 was administered daily. ANC and marrow pathology were compared between saline and HQK-1002S-treated animals. The duration of peripheral neutropenia was similar in controls and HQK-1002S-treated animals, but bone marrow pathology demonstrated profound ablation of all mature myeloid series (10-20% cellularity) in the saline controls, while HQK-1002S-treated animals had normal bone marrow cellularity (55–75%) with complete neutrophil maturation within 2 weeks following radiation. In 5FU-treated mice, neutrophil recovery was compared between HQK-1002, saline, or G-CSF treatment for 3 weeks. Recovery from profound neutropenia (nadir at Day 9) occurred by Day 13 in G-CSF- and HQK-1002 treated animals, 5 days before recovery was observed in saline controls. HQK-1002 and HQK-1002S were also administered to non-irradiated, normal juvenile baboons, once daily for 5 days, and CBCs and neutrophil counts were assayed. HQK-1002 or HQK-1002S treatment in 3 unchallenged baboons resulted in a two-fold to three-fold rises in ANC within 7 days. Collectively, these studies strongly suggest that HQK-1002 and HQK-1002S, orally-bioavailable SCFADs, stimulate myelopoiesis in vivo in normal animals and during sub-lethal radiation-induced bone marrow suppression, and merit further evaluation in neutropenia associated with marrow suppression.