Session: 625. Lymphoma: Pre-Clinical—Chemotherapy and Biologic Agents: Poster I
Hematology Disease Topics & Pathways:
Diseases, Non-Biological, Mantle Cell Lymphoma, Therapies, Non-Hodgkin Lymphoma, Lymphoid Malignancies
CG-806 is a BTK/cluster-selective kinase inhibitor currently under investigation in phase 1 clinical trials for patients with hematological malignancies. CG-806 targets both WT BTK (IC50 ~ 8 nM) and the BTKC481S (IC50 ~ 2.5 nM; www.aptose.com). Here we investigate the anti-tumor effects of CG-806 in mantle cell lymphoma (MCL) and diffuse large B cell lymphoma (DLBCL).
Methods: CG-806 was provided by Aptose Biosciences, Inc. (San Diego, CA). DLBCL and MCL cell lines were assayed for apoptosis/proliferation, metabolic phenotype (Seahorse), mitochondrial mass and mitophagy. Ibrutinib (ibr) resistance was induced by exposure over 6 months. Primary peripheral blood mononuclear cells were incubated for 24 h in media conditioned by stromal cells engineered to express CD40L or BAFF prior to drug treatment. Two MCL PDX models were used (chemo-resistant and ibr-resistant). MCL cells were injected into the tail vein of NSG mice and tracked weekly by flow cytometry (CD5+ CD19+ CD45+). Upon MCL detection in the peripheral blood, mice began daily treatment with 30.8 or 308 mg/kg CG-806 or vehicle control via oral gavage until moribund. Splenocytes were harvested 1 h after the final drug treatment.
Results: CG-806 potently inhibited proliferation of both parental and ibr-resistant MCL cell lines (Mino, JeKo-1) with IC50<0.01 μM at 72 h. DLBCL cell lines (U2932, OCI-LY3 OCI-LY19) demonstrated moderate sensitivity to CG-806 (IC50 0.3-1 μM), while SU-DHL10 was highly sensitive (IC50<0.01 µM). Treatment with CG-806, but not ibrutinib, induced apoptosis of primary MCL cells in CD40L- or BAFF-expressing stromal co-cultures. Following anti-IgM crosslinking of primary cells, treatment with CG-806 decreased phosphorylation of SYK, BTK, AKT and ERK, indicating disrupted BCR signaling.
Treatment with CG-806 increased respiratory reserve capacity but did not impact the basal oxygen consumption rate in both parental and ibr-resistant MCL cell lines. Basal extracellular acidification rate (ECAR) was increased following CG-806 treatment, indicating heightened glycolytic activity. Furthermore, CG-806-treated cells demonstrated potent induction of mitophagy accompanied by a reduction in mitochondrial mass.
CG-806 slowed expansion of circulating MCL cells and reduced proliferation of spleen-resident MCL cells in both chemo- and ibr-resistant MCL PDX models. CG-806 and ibrutinib extended survival of chemoresistant PDX mice without evidence of toxic events. Treatment with CG-806 led to decreased phosphorylation of SYK, BTK, and AKT but also upregulated expression of BCL2 and BCLX. RNA-seq analysis of spleen-resident cells revealed downregulation of NFκB targets and JAK/STAT signaling in ibr-resistant PDX mice treated with CG-806. This was accompanied by enrichment of metabolic pathways (oxidative phosphorylation, fatty acid metabolism) and MYC targets.
Next, we evaluated CG-806 for synthetic lethality in a functional in vitro screening assay using a panel of 189 small molecule inhibitors that target a variety of distinct signaling pathways activated in cancer (Tyner et al, 2018). Consistent with the above observations, synergy was observed between CG-806 and inhibitors of metabolic enzymes (teleglenastat, perhexiline maleate) and BH3-mimetics targeting BCL2/X proteins (venetoclax, AZD4320).
Conclusions: Our data demonstrate preliminary efficacy of CG-806 in MCL and DLBCL in vitro and in MCL DPX models. CG-806 treatment led to metabolic reprograming towards glycolysis and induced mitophagy. BCL2 family proteins may be implicated in resistance to CG-806. These results provide rationale for further investigation of CG-806 in aggressive NHL.
Disclosures: Tyner: Array: Research Funding; AstraZeneca: Research Funding; Constellation: Research Funding; Genentech: Research Funding; Incyte: Research Funding; Janssen: Research Funding; Petra: Research Funding; Seattle Genetics: Research Funding; Syros: Research Funding; Takeda: Research Funding; Gilead: Research Funding; Agios: Research Funding; Aptose: Research Funding. Danilov: Pharmacyclics: Consultancy; Astra Zeneca: Consultancy, Research Funding; Verastem Oncology: Consultancy, Research Funding; Takeda Oncology: Research Funding; Gilead Sciences: Research Funding; Bayer Oncology: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; TG Therapeutics: Consultancy; Nurix: Consultancy; Celgene: Consultancy; Aptose Biosciences: Research Funding; Bristol-Myers Squibb: Research Funding; Rigel Pharmaceuticals: Consultancy; Karyopharm: Consultancy; BeiGene: Consultancy; Abbvie: Consultancy.
See more of: Oral and Poster Abstracts