Abstract 3942: Novel BCL2 inhibitors with anti-lymphoma activity

Background: Diffuse large B cell lymphomas (DLBCLs) are aggressive tumors that account for almost half of all lymphoma incidences. In particular, double-hit and triple-hit DLBCLs, with translocations involving BCL2, MYC and/or BCL6, have a very poor prognosis and occur in up to 7% of cases. Double expressor DLBCLs, with overexpression of BCL2 and MYC in the absence of chromosomal translocations, also have a poor prognosis. BCL2 inhibitors (BCL2i) have shown preclinical and clinical efficacy in lymphomas. Here, we synthesized and tested seven novel BCL2i in DLBCL cells with deregulated BCL2, and splenic marginal zone lymphoma (SMZL) cell lines with acquired resistance to idelalisib, copanlisib or ibrutinib.

Methods: Using in silico-based drug design complemented by classical and kinetic target-guided synthesis (KTGS) led to the synthesis of seven potential BCL2 inhibitors (BCL2i). The MTT assay was used to assess the anti-proliferative activities of BCL2i: ST-59, ST-64, ST-65, R, Z-89, Z-103, Z-116-8 in BCL2-translocated DLBCLs: SU-DHL-4, Toledo, DOHH2, KARPAS422, WSUDLCL2, Pfeiffer; BCL2 amplified DLBCL: U2932 and resistant SMZLs. Cells were treated with increasing concentrations of BCL2i for 72 hours [h].

Results: Median IC50 values for the seven BCL2i ranged from 22 μM to 49 μM. ST-65 was the most potent BCL2i (range = 12 - 46 μM, median = 22 μM), showing anti-proliferative activity in DLBCL and SMZL. The other BCL2i were inactive in at least 2 cell lines (IC50 > 50 μM). The three least potent BCL2i were Z-89, Z-103 and R (median IC50 = 49, 44 and 45 μM, respectively). ST-65 was the only BCL2i synthesized by BCL2 using KTGS, indicating KTGS as a superior technique for generating BCL2i. The poor activity of R agreed with its inability to cross the cell membrane as determined by liquid chromatography-mass spectrometry. Among the resistant SMZLs, parental KARPAS1718 were most sensitive to the BCL2i, responding to 5 out of 7 inhibitors (range = 11 - 47 μM, median = 22 μM). The activated B cell like (ABC)-DLBCL, U2932, was only sensitive to ST-65 (IC50 = 20 μM). U2932 lacks translocated BCL2, but BCL2 is amplified and overexpressed in this cell line.

Conclusions: We report the in vitro anti-lymphoma activities of novel BCL2i, particularly ST-65, in DLBCL and SMZL cells. Our results suggest that these compounds are structures further exploitable for the design of improved anti-lymphoma drugs.

Acknowledgements: The research work was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: 991 to AGT).

Citation Format: Afua Adjeiwaa Mensah, Christos M. Chatzigiannis, Dimitrios A. Diamantis, Vasileios K. Gkalpinos, Alberto Arribas, Andreas G. Tzakos, Francesco Bertoni. Novel BCL2 inhibitors with anti-lymphoma activity [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 3942.

Bioinspired tailoring of fluorogenic thiol responsive antioxidant precursors to protect cells against H2O2-induced DNA damage

Natural antioxidants, like phenolic acids, possess a unique chemical space that can protect cellular components from oxidative stress. However, their polar carboxylic acid chemotype reduces full intracellular antioxidant potential due to limited diffusion through biological membranes. Here, we have designed and developed a new generation of hydrophobic turn-on fluorescent antioxidant precursors that upon penetration of the cell membrane, reveal a more polar and more potent antioxidant core and simultaneously become fluorescent allowing their intracellular tracking. Their activation is stimulated by polarity alteration by sensing intracellular signals and specifically biothiols. In our design, the carboxylic group of phenolic acids that originally restricts cell entrance is derivatized and conjugated through Copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) to a coumarin derivative that its fluorescence properties are quenched with a biothiol activatable element. This more hydrophobic precursor readily penetrates cell membrane and once inside the cell the antioxidant core is revealed upon sensing glutathione, its fluorescence is restored in a turn-on manner and the generation of a more polar character traps the molecule inside the cell. This turn-on fluorescent antioxidant precursor that can be applied to phenolic acids, was developed for rosmarinic acid and the conjugate was named as RCG. The selectivity and responsiveness of RCG towards the most abundant biothiols was monitored through a variety of biophysical techniques including UV-Vis, fluorescence and NMR spectroscopy. The electrochemical behavior and free radical scavenging capacity of the precursor RCG and the active compound (RC) was evaluated and compared with the parent compound (rosmarinic acid) through cyclic voltammetry and EPR spectroscopy, respectively. The stability of the newly synthesized bioactive conjugate RC was found significantly higher than the parent rosmarinic acid when exposed to oxygen. Cell uptake experiments were conducted and revealed the internalization of RCG. The degree of intracellular DNA protection offered by RCG and its active drug (RC) on exposure to H₂O₂ was also evaluated in Jurkat cells.

Preparation and Biophysical Characterization of Quercetin Inclusion Complexes with β-Cyclodextrin Derivatives to be Formulated as Possible Nose-to-Brain Quercetin Delivery Systems

Quercetin (Que) is a flavonoid associated with high oxygen radical scavenging activity and potential neuroprotective activity against Alzheimer's disease. Que's oral bioavailability is limited by its low water solubility and extended peripheral metabolism; thus, nasal administration may be a promising alternative to achieve effective Que concentrations in the brain. The formation of Que-2-hydroxypropylated-β-cyclodextrin (Que/HP-β-CD) complexes was previously found to increase the molecule's solubility and stability in aqueous media. Que-methyl-β-cyclodextrin (Que/Me-β-CD) inclusion complexes were prepared, characterized, and compared with the Que/HP-β-CD complex using biophysical and computational methods (phase solubility, fluorescence and NMR spectroscopy, differential scanning calorimetry (DSC), and molecular dynamics simulations (MDS)) as candidates for the preparation of nose-to-brain Que's delivery systems. DSC thermograms, NMR, fluorescence spectroscopy, and MDS confirmed the inclusion complex formation of Que with both CDs. Differences between the two preparations were observed regarding their thermodynamic stability and inclusion mode governing the details of molecular interactions. Que's solubility in aqueous media at pH 1.2 and 4.5 was similar and linearly increased with both CD concentrations. At pH 6.8, Que's solubility was higher and positively deviated from linearity in the presence of HP-β-CD more than with Me-β-CD, possibly revealing the presence of more than one HP-β-CD molecule involved in the complex. Overall, water solubility of lyophilized Que/Me-β-CD and Que/HP-β-CD products was approximately 7-40 times and 14-50 times as high as for pure Que at pH 1.2-6.8. In addition, the proof of concept experiment on ex vivo permeation across rabbit nasal mucosa revealed measurable and similar Que permeability profiles with both CDs and negligible permeation of pure Que. These results are quite encouraging for further ex vivo and in vivo evaluation toward nasal administration and nose-to-brain delivery of Que.

Valorisation of stachysetin from cultivated Stachys iva Griseb. as anti-diabetic agent: a multi-spectroscopic and molecular docking approach

Stachys species are considered as important medicinal plants with numerous health benefit effects. In continuation of our research on the Greek Stachys species, the chemical profile of the aerial parts of cultivated S. iva Griseb. has been explored. The NMR profiles of the plant extract/infusion were used to guide the isolation process, leading to the targeted isolation of seventeen known compounds. The rare acylated flavonoid, stachysetin, was isolated for the third time from plant species in the international literature. Identification of the characteristic signals of stachysetin in the 1D ¹H-NMR spectrum of the crude extract was presented. In order to evaluate the potential of the identified chemical space in Stachys to bear possible bioactivity against diabetes, we performed an in silico screening against 17 proteins implicated in diabetes, as also ligand based similarity metrics against established anti-diabetic drugs. The results capitalized the anti-diabetic potency of stachysetin. Its binding profile to the major drug carrier plasma protein serum albumin was also explored along with its photophysical properties suggesting that stachysetin could be recognized and delivered in plasma through serum albumin and also could be tracked through near-infrared imaging. Communicated by Ramaswamy H. Sarma.

Lipophilic ester and amide derivatives of rosmarinic acid protect cells against H2O2-induced DNA damage and apoptosis: The potential role of intracellular accumulation and labile iron chelation

Phenolic acids represent abundant components contained in human diet. However, the negative charge in their carboxylic group limits their capacity to diffuse through biological membranes, thus hindering their access to cell interior. In order to promote the diffusion of rosmarinic acid through biological membranes, we synthesized several lipophilic ester- and amide-derivatives of this compound and evaluated their capacity to prevent H2O2-induced DNA damage and apoptosis in cultured human cells. Esterification of the carboxylic moiety with lipophilic groups strongly enhanced the capacity of rosmarinic acid to protect cells. On the other hand, the amide-derivatives were somewhat less effective but exerted less cytotoxicity at high concentrations. Cell uptake experiments, using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS), illustrated different levels of intracellular accumulation among the ester- and amide-derivatives, with the first being more effectively accumulated, probably due to their extensive hydrolysis inside the cells. In conclusion, these results highlight the hitherto unrecognized fundamental importance of derivatization of diet-derived phenolic acids to unveil their biological potential.