Preclinical evaluation of apoptosis induction by the novel small molecule BCL-2 inhibitor, GX015–070, in ex vivo chronic lymphoid leukemia (CLL) cells

Abstract

3149 Background: CLL is associated with loss of normal cellular apoptotic function. Apoptosis in cell lines has been identified with GX015–070 (GX), a small molecule antagonist of the BH3-binding groove of the BCL-2 family of proteins which is frequently overexpressed in cancers including CLL. This study evaluated GX induced apoptosis in CLL cells ex vivo correlating it with prognostic factors. Methods: Circulating lymphocytes were collected from patients (pts) with ≥ 20x109/L lymphocytes with no CLL treatment or red cell transfusions within 4 wks. Medical history was recorded. The diagnosis was confirmed with immunophenotyping by flow cytometry. CD38 was assessed in this analysis. The cytogenetic abnormalities del(11q), +12, del(13)(q14.3), del(13)(q34) & del(17p) were established by fluorescent in situ hybridization. Apoptosis was assessed with surface annexin V immunophenotyping in B cell enriched samples with positive glucocorticoid and negative DMSO controls. Results: 30 pts were recruited including 67% men with median age of 65 yrs (range 43–83). Rai stages were 6 stage 0; 8 stage 1; 6 stage 2; 4 stage 3; and 6 stage 4. Median lymphocyte count was 37.6x109/L (19.4–204.5). Prior treatment included 0–4 regiments (median 0). Previous treatments were alkylating agents (13%), purine analogues (13%), both (13%) and campath after both (3%). 33% of pts (n=10) expressed CD38. Cytogenetic analysis showed no abnormalities in 20%, del(11q) in 17%, +12 in 10%, -12 in 3%, del(13)(q14.3) in 53%, del(13)(q34) in 3% and no del(17p). ≥ 1 abnormality was seen in 4 pts. Apoptosis testing was performed and controls appropriate in 28 samples. All (100%) had significant early apoptosis with GX. A dose response to GX was found in all pts. The greatest % of annexin positive cells was observed at 6 hrs with 5 uM. In the last 12 pts, rescue from early apoptosis induction with IL-4 was observed in all glucocorticoid treated but in none of the GX treated cells. Conclusions: GX results in early and vigorous induction in vitro apoptosis of CLL cells. This population had both good & poor prognostic clinical factors. GX is one of the few agents where IL-4 co-treatment does not inhibit the induction of apoptosis. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration GeminX, GeminX Biotech