VIP152 is a selective CDK9 inhibitor with pre-clinical in vitro and in vivo efficacy in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is effectively treated with targeted therapies including Bruton tyrosine kinase inhibitors and BCL2 antagonists. When these become ineffective, treatment options are limited. Positive transcription elongation factor complex (P-TEFb), a heterodimeric protein complex composed of cyclin dependent kinase 9 (CDK9) and cyclin T1, functions to regulate short half-life transcripts by phosphorylation of RNA Polymerase II (POLII). These transcripts are frequently dysregulated in hematologic malignancies; however, therapies targeting inhibition of P-TEFb have not yet achieved approval for cancer treatment. VIP152 kinome profiling revealed CDK9 as the main enzyme inhibited at 100 nM, with over a 10-fold increase in potency compared with other inhibitors currently in development for this target. VIP152 induced cell death in CLL cell lines and primary patient samples. Transcriptome analysis revealed inhibition of RNA degradation through the AU-Rich Element (ARE) dysregulation. Mechanistically, VIP152 inhibits the assembly of P-TEFb onto the transcription machinery and disturbs binding partners. Finally, immune competent mice engrafted with CLL-like cells of Eµ-MTCP1 over-expressing mice and treated with VIP152 demonstrated reduced disease burden and improvement in overall survival compared to vehicle-treated mice. These data suggest that VIP152 is a highly selective inhibitor of CDK9 that represents an attractive new therapy for CLL.

Preclinical evaluation of combination nemtabrutinib and venetoclax in chronic lymphocytic leukemia

Inhibitors of B cell receptor (BCR) signaling such as the Bruton's tyrosine kinase (BTK) inhibitors are effective therapeutics for chronic lymphocytic leukemia (CLL). The first-in-class covalent BTK inhibitor, ibrutinib, produces durable responses in most CLL patients; however, complete responses are only observed in a minority of patients. B cell lymphoma 2 (BCL2), an anti-apoptotic protein that contributes to CLL cell survival, has also been investigated as a therapeutic target. The BCL2 inhibitor venetoclax is effective in patients with CLL and can produce undetectable minimal residual disease, allowing discontinuation of therapy. In combination, ibrutinib and venetoclax have shown preclinical synergy and clinical efficacy. Nemtabrutinib is a next generation, reversible inhibitor of BTK that potently inhibits BCR signaling in treatment-naïve and ibrutinib-refractory CLL cells ex vivo. The clinical efficacy of combining BTK inhibitors with BCL2 inhibitors motivated us to evaluate the novel combination of nemtabrutinib and venetoclax. In vitro studies show that nemtabrutinib and venetoclax are not antagonistic to each other. In an adoptive transfer CLL mouse model, mice treated with nemtabrutinib and venetoclax had prolonged survival compared to mice treated with ibrutinib and venetoclax. Our preclinical studies further validate the combination of BTK inhibitors with venetoclax and justify further investigation of combining nemtabrutinib with venetoclax in CLL.

Abstract 1031: PRMT5 inhibition alters mitochondrial dynamics in mantle cell lymphoma, creating vulnerability to BH3 mimetic compounds

Mantle cell lymphoma (MCL) is an aggressive and incurable blood cancer comprising 5% of all non-Hodgkin lymphomas diagnosed annually. The median age of diagnosis is 68yo, and while many patients initially respond to frontline treatment, relapse is common. There is an unmet need to develop novel therapeutic strategies for the treatment of MCL. Our group has identified protein arginine methyltransferase 5 (PRMT5) as a key driver of MCL pathogenesis. PRMT5 symmetrically dimethylates arginine residues on a number of proteins (P53, E2F1, P65) and histones (H4R3, H3R8, H2AR3), which support tumorigenesis. Selectively inhibiting PRMT5 has shown significant anti-tumor activity in preclinical MCL models, and a Phase 1 clinical trial with PRT543 (Prelude), a novel PRMT5 inhibitor, is underway. While exploring pathways that converge with PRMT5 activity as potential avenues for combination treatment, we identified the intrinsic apoptotic pathway as an attractive target in MCL. BCL2 family proteins either promote or inhibit intrinsic apoptosis at the outer mitochondrial membrane through a dynamic set of binding interactions. Prior work has shown PRMT5 inhibition to drive the expression of multiple pro-death BCL2 family gene products (BAX, BAK, and BBC3/PUMA) in MCL. We hypothesized that combining PRMT5 inhibition with BH3 mimetics, compounds that target pro-survival BCL2 proteins, would induce synergistic cell death in MCL. Selective PRMT5 inhibition with PRT382 inhibits the viability of MCL cell lines with an IC50 below 1uM in eight of nine lines (IC50 44.8nM - 1905.5nM). BH3 mimetics navitoclax (BCL2, BCLXL, and BCLw inhibitor), A852 (BCLXL inhibitor), and AMG176 (MCL1 inhibitor) were found to have IC50s below 1uM in five, two, and four of the nine cell lines respectively. We chose six cell lines to test combination treatment ranging in sensitivity to BH3 mimetics and expression of BCL2 family proteins (CCMCL1, Z-138, UPN1, Granta 519, Mino, and Maver1). Synergistic decreases in viability were tested via MTS assay and analyzed with the Loewe model of synergy. Mino, which showed sensitivity to all three mimetics, exhibited a synergistic reduction in viability with combination PRT382 treatment. Granta 519 and Z-138 exhibited a similar effect with the combination of PRT382 and navitoclax or A852. These observations were confirmed through BH3 profiling, supporting MCL cell line dependence on BCL2, BCLXL, BCLw and MCL1, and increased sensitivity to BCL2 family protein targeting with PRMT5 inhibition. Two patient derived xenograft models were tested ex vivo after treatment with 10mg/kg of the PRMT5 inhibitor PRT382 or vehicle. iBH3 flow-based analysis revealed increased sensitivity of ex vivo PDX cells to pan BCL2, BCLXL, and MCL1 inhibition. These results provide rationale for combining BH3 mimetics and PRMT5 inhibition in clinical trials as a novel treatment strategy for MCL.

Citation Format: Claire Hinterschied, Fiona Brown, Janani Ravikrishnan, JoBeth Helmig-Mason, Kris Vaddi, Peggy Scherle, Jennifer Woyach, Selina Chen-Kiang, Oliver Elemento, Jihye Paik, Robert Baiocchi. PRMT5 inhibition alters mitochondrial dynamics in mantle cell lymphoma, creating vulnerability to BH3 mimetic compounds [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1031.

Manipulation of the sodium-potassium ratio as a lever for controlling cell growth and improving cell specific productivity in perfusion CHO cell cultures

Perfusion processes typically require removal of a continuous or semi-continuous volume of cell culture in order to maintain a desired target cell density. For fast growing cell lines, the product loss from this stream can be upwards of 35%, significantly reducing the overall process yield. As volume removed is directly proportional to cell growth, the ability to modulate growth during perfusion cell culture production thus becomes crucial. Leveraging existing media components to achieve such control without introducing additional supplements is most desirable because it decreases process complexity and eliminates safety and clearance concerns. Here, the impact of extracellular concentrations of sodium (Na) and potassium (K) on cell growth and productivity is explored. High throughput small-scale models of perfusion revealed Na:K ratios below 1 can significantly suppress cell growth by inducing cell cycle arrest in the G0/1 phase. A concomitant increase in cell specific productivity was also observed, reaching as high as 115 pg/cell/day for one cell line studied. Multiple recombinant Chinese hamster ovary (CHO) cell lines demonstrated similar responses to lower Na:K media, indicating the universal applicability of such an approach. Product quality attributes were also assessed and revealed that effects were cell line specific, and can be acceptable or manageable depending on the phase of the drug development. Drastically altering Na and K levels in perfusion media as a lever to impact cell growth and productivity is proposed.

Leukemoid like reaction in a post CABG patient

The presentation of leukemoid reaction in patients post-cardiac surgery is rare with limited prior reports in the English language literature. We report a case of raised leukocyte count with no evidence of infection in a patient post coronary artery bypass graft surgery. The exaggerated inflammatory response by the patient to extra-corporeal circulation was drastically elevated, but fell short of the leukaemoid reaction definition – so we have defined it as a leukaemoid like reaction. A clear correlation between the extra-corporeal circulation and inflammatory response is documented.

A comparative study of the efficacy of topical negative pressure moist dressings and conventional moist dressings in chronic wounds

Aim: To assess the efficacy of topical negative pressure moist wound dressing as compared to conventional moist wound dressings in improving the healing process in chronic wounds and to prove that negative pressure dressings can be used as a much better treatment option in the management of chronic wounds. Materials and Methods: This is a prospective comparative study of data from 112 patients with chronic wounds, of which 56 patients underwent topical negative pressure dressings (17 diabetic, 10 pressure sores, nine ischemic, two varicose, 10 post-infective raw areas and eight traumatic - six had bone exposed, two orthopaedic prosthesis exposed). The remaining 56 patients underwent conventional moist dressings (20 diabetic, two ischemic, 15 pressure sores, three varicose, eight post-infective raw areas and eight traumatic - five had bone exposed, three orthopaedic prosthesis exposed). The results were compared after 10 days. The variables compared were, rate of granulation tissue formation as a percentage of ulcer area covered, skin graft take up as the percentage of ulcer surface area and duration of hospital stay. The variables were compared using Unpaired Student′s t test. A " P" value < 0.05 was considered significant. Results: Out of 56 patients who underwent topical negative pressure dressings, six (10.71%) were failures, due to failure in maintaining topical negative pressure due to defective sealing technique; these were included into the study group. After 10 days, the mean rate of granulation tissue formation was 71.43% of ulcer surface area. All these 56 cases underwent split-thickness skin grafting. The mean graft take-up was 79.29%. The mean hospital stay was 32.64 days. In the remaining 56 patients, the mean rate of granulation tissue formation was 52.85% of ulcer surface area. The mean graft take-up was only 60.45% of the total ulcer surface area. The mean hospital stay was 60.45 days. Conclusion: To conclude, topical negative pressure dressings help in faster healing of chronic wounds and better graft take-up and reduce hospital stay of these patients.

Fournier′s gangrene of the penis

Fournier′s gangrene is a rare, fulminant, though generally localized disease of the scrotum and penis with occasional extension up the abdominal wall. The usual organism is an anaerobic streptococcus synergistic with some second organism. Our case was unusual in that only the penis was involved without involving the scrotum or abdominal wall. Early therapy is the key, including hospitalization, debridement of entire shaft of the penis distal to the devasted area without excising the normal skin, parenteral broad-spectrum antibiotics & skin grafting. Only few cases of Fournier′s gangrene of the penis have been reported.