Inhibitor In Clinical Development Research Articles

Abstract PO1-04-14: PLK1 Inhibitor Onvansertib Extends the Response and Overcomes Resistance to Paclitaxel in Palbociclib-resistant HR+ Breast Cancer Patient-derived Xenografts

Abstract Paclitaxel is a first-line chemotherapy for hormone receptor positive (HR+) metastatic breast cancer patients after progression on a combination of endocrine and CDK4/6 inhibitor therapy. Response rate to paclitaxel ranges between 20-40%, and most patients progress due to intrinsic or acquired resistance, leaving them with limited treatment choices. Therapeutic strategies to overcome paclitaxel resistance and extend its clinical benefit are urgently needed. Paclitaxel-resistant tumors have increased expression of polo-like kinase 1 (PLK1), a serine-threonine-protein kinase that regulates mitosis and cell cycle progression. PLK1 has also been shown to mediate resistance to CDK4/6 inhibitor palbociclib in HR+ breast cancer. Onvansertib is an orally bioavailable, highly potent, and selective PLK1 inhibitor in clinical development. Onvansertib exhibited synergy in vitro and showed potent anti-tumor activity in vivo in combination with paclitaxel in ovarian cancer and triple negative breast cancer (TNBC) preclinical models. A phase 1b/2 clinical trial is ongoing to evaluate the safety and efficacy of onvansertib plus paclitaxel in advanced TNBC (NCT05383196). Here we investigated whether the potential of onvansertib and paclitaxel combination could be extended to HR+ breast cancer. Co-treatment with onvansertib and paclitaxel synergistically inhibited the viability of HR+ breast cancer cell lines (MCF-7, T-47D, EFM-19, CAMA-1, ZR-75-1). Compared to the single agents, the combination induced increased apoptosis. The combination was further tested in vivo in patient-derived xenograft (PDX) models. To this end, six HR+ breast cancer PDXs with intrinsic or acquired resistance to palbociclib were established from primary breast tumors (n=1) or metastatic bone biopsies (n=5). The PDX tumors were engrafted subcutaneously in nude mice and the effect of onvansertib (45 mg/kg, oral, 5 days a week) and paclitaxel (15-25mg/kg, IP, once a week) was investigated as monotherapy and in combination. The combination of onvansertib and paclitaxel was tolerated with minimal toxicity and showed enhanced anti-tumor activity compared to either agent alone in all 6 PDX models. Paclitaxel and onvansertib monotherapies had little to no anti-tumor activity in 4 out of 6 PDX models (HBCx124palboR25, HBCx-139 palboR5, HBCx-202 and HBCx-131). Importantly, the combination of onvansertib and paclitaxel induced strong anti-tumor activity in these 4 models. Tumor regression was observed in the 2 PDX models with acquired resistance to palbociclib, HBCx-124palboR25 and HBCx-139palboR5, with 62% (5/8 mice) and 54% (6/11 mice) complete response rates, respectively. The combination showed tumor stasis in HBCx-131 and induced tumor regression in HBCx-202, established from patient resistant to palbociclib. In 2 of the 6 PDXs, paclitaxel exhibited anti-tumor activity, inducing tumor regression in HBCx-137paboR26 and tumor stasis in HBCx-86. In comparison, the combination of onvansertib and paclitaxel had greater activity, inducing tumor regression in both models with a higher rate of complete response than the monotherapy. Complete response rates for paclitaxel versus the combination were 62% and 100% in the HBCx-137palboR26 model and 0% and 67% in the HBCx-86 model. Notably, the antitumor activity of the onvansertib and paclitaxel combination was very durable, showing a robust delay in tumor relapse after stopping therapy. Together, our data strongly support that combining paclitaxel with the PLK1 inhibitor onvansertib extends its benefit and overcomes paclitaxel resistance, and represents a promising therapeutic strategy for HR+ breast cancer patients after progression on a combination of endocrine and CDK4/6 inhibitor therapy. Citation Format: Maya Ridinger, Pierre Painsec, Sreeja Sreekumar, Dalia Gonzalez, Davis Klein, Laura Sourd, Elodie Montaudon, Paul Cottu, Tod Smeal, Elisabetta Marangoni. PLK1 Inhibitor Onvansertib Extends the Response and Overcomes Resistance to Paclitaxel in Palbociclib-resistant HR+ Breast Cancer Patient-derived Xenografts [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-04-14.

Identification and Biosynthesis of an N-Glucuronide Metabolite of Camonsertib.

Camonsertib is a novel ATR kinase inhibitor in clinical development for advanced cancers targeting sensitizing mutations. This article describes the identification and biosynthesis of an N-glucuronide metabolite of camonsertib. This metabolite was first observed in human hepatocyte incubations and was subsequently isolated to determine the structure, evaluate its stability as part of bioanalytical method development and for use as a standard for estimating its concentration in Phase I samples. The N-glucuronide was scaled-up using a purified bacterial culture preparation and was subsequently isolated using preparative chromatography. The bacterial culture generated sufficient material of the glucuronide to allow for one- and two-dimensional 1H and 13C NMR structural elucidation and further bioanalytical characterization. The NOE data combined with the gradient HMBC experiment and molecular modeling, strongly suggests that the point of attachment of the glucuronide results in the formation of (2S,3S,4S,5R,6R)-3,4,5-trihydroxy-6-(5-(4-((1R,3r,5S)-3-hydroxy-8-oxabicyclo[3.2.1]octan-3-yl)-6-((R)-3-methylmorpholino)-1H-pyrazolo[3,4-b]pyridin-1-yl)-1H-pyrazol-1-yl)tetrahydro-2H-pyran-2-carboxylic acid. Significance Statement This is the first report of a glucuronide metabolite of camonsertib formed by human hepatocyte incubations. This study reveals the structure of an N-glucuronide metabolite of camonsertib using detailed elucidation by one- and two-dimensional NMR after scale-up using a novel bacterial culture approach yielding significant quantities of a purified metabolite.

Covalent Menin Inhibitor Bmf-219 in Patients with Relapsed or Refractory (R/R) Acute Leukemia (AL): Preliminary Phase 1 Data from the Covalent-101 Study

Background: Menin, a protein involved in transcriptional regulation, plays a role in the genesis of multiple cancers. Preclinical data from BMF-219, an investigational, highly selective, oral small-molecule inhibitor of menin, show sustained potent abrogation of menin-dependent oncogenic signaling. BMF-219 is the first and only covalent menin inhibitor in clinical development and is being evaluated in multiple hematologic malignancies, solid tumors, and diabetes mellitus. COVALENT-101 (NCT05153330) is a Phase I dose-escalation and -expansion study of BMF-219 in R/R AL (Cohort 1), DLBCL (Cohort 2), MM (Cohort 3), and CLL (Cohort 4). Here we report preliminary safety, PK and anticancer activity data from Cohort 1 (AL). Methods: Doses of BMF-219 are escalated independently for each indication, initially in single-subject cohorts followed by a “3 + 3” design. Eligible patients (pts) include adults with R/R AL ineligible for standard therapy. Initially pts were enrolled agnostic to molecular status. A subsequent amendment introduced quotas for KMT2Ar (MLL1r), NPM1 and other known menin-dependent mutations: CEBP/A, MLL1-PTD, MN1, NUP98, NUP214, PICALM-AF10, SETBP1. Prior exposure to reversible menin inhibitor therapy is permitted. Subjects receive BMF-219 daily for continuous 28-day cycles until progression/intolerability. There are 2 parallel dose-escalation arms: pts not taking (Arm A) or taking (Arm B) moderate or strong CYP3A4 inhibitors. The study is ongoing and accruing in the escalation. Expansion cohorts will enroll pts to obtain further safety and efficacy data at the OBD/RP2D. Results: As of data cutoff of 7/24/2023, 26 pts with R/R AL (24 AML; 2 ALL) are enrolled; 7 remain on study treatment. Baseline characteristics include 17(65%) males and 9(35%) females with a median age of 57.5 years (range 33-84). There is a median of 4 (range 1-8) prior lines of therapy and 11 (42%) with prior HSCT(s). Six pts (23%) had KMT2Ar, 3 (12%) KMT2A-PTD, 4 (15%) NPM1, and 13 (50%) WT for KMT2A and NPM1. Dosing began with single-patient cohorts at 100 mg QD (Arm A) and 25 mg QD (Arm B) and has been escalated through 4 dose levels. Thus far, pts have been dosed up to 500 mg QD (Arm A) and 125 mg QD (Arm B). BMF-219 exposures were comparable between arms, with ~2-4-fold higher exposures observed with co-administration of a moderate or strong CYP3A4 inhibitor. At the highest dose (DL4) in which PK was evaluated, Arm A (500 mg QD) and Arm B (125 mg QD), pts on average achieved ~50% of target exposure (2000 ng*hr/mL) with some pts surpassing it. Higher QD dosing or corresponding BID dosing is expected to achieve desired exposure. BMF-219 has generally been well tolerated with no DLTs observed and no discontinuations due to treatment-related toxicities. No related QTc prolongation was observed. At the time of data cutoff, 23 of 26 pts were included in the safety population. Common TRAEs (≥10%) include vomiting 13% (3) and Differentiation Syndrome (DS) 13% (3). No Grade 5 TRAEs were reported. The only common Grade ≥3 TRAE (≥5%) was DS 13% (3). The efficacy evaluable population includes AML pts who meet the following criteria: dosed at or near predicted efficacious dose (500 mg or above [Arm A]; 125 mg or above [Arm B]), had known menin-dependent mutations, and completed at least one scheduled response assessment (or had a minimum of 7 doses if discontinued prematurely). Thus far, 2 of 5 efficacy evaluable patients achieved a complete remission (1 CR; 1 CRi) and both continue BMF-219 treatment. Patient A: 39/M, NUP98-NSD1, ECOG=0, 500 mg QD, Arm A, 4 prior lines of treatment including intensive chemotherapy and allo-HSCT. At C1D27, marrow blasts were reduced to 6% from 13% at study entry. The patient achieved CR at C2D28 with 0% blasts.Patient B: 70/F, NPM1m, ECOG=1, 125 mg QD, Arm B, 1 prior line of treatment with decitabine and an investigational agent. At C1D28, marrow blasts were reduced to 34% from 52% at study entry. The patient achieved CRi with 3% blasts at C2D28. Conclusion: BMF-219 is generally well tolerated with no DLT observed (and able to be taken with and without CYP3A4 inhibitors) with no pts discontinuing therapy due to toxicity. BMF-219 dose escalation is ongoing and approaching target exposure. BMF-219 demonstrates early signs of clinical activity in different genomic subgroups. The trial is ongoing and includes enrollment for pts diagnosed with AL, DLBCL, MM and CLL.

HPLC with Post-Column Derivatization with Alizarin for Determination of OATD-02, an Anticancer Arginase Inhibitor in Clinical Development

The aim of this study was to develop an analytical method for selective determination of OATD-02 by high-performance liquid chromatography (HPLC) with post-column derivatization and fluorescence detection (FLD). OATD-02, a new boronic acid derivative, is a highly potent anticancer arginase inhibitor in clinical development. Chromatographic analysis of OATD-02 poses problems because this molecule has weak ultraviolet absorption. The derivatization reaction was based on the reaction between boronic acid from OATD-02 and alizarin solution. The optimized mobile phase consisted of a mixture of sodium bicarbonate in water and acetonitrile at a flow rate of 0.50 mL/min. Alizarin solution in methanol was delivered at a flow rate of 0.50 mL/min. The fluorescent complexes were detected by a fluorescence detector (excitation and emission wavelengths at 470 and 580 nm, respectively). The present method demonstrated proper values for selectivity, linearity, recovery (>99%), precision (RSD: 0.6%), sensitivity (LOD: 20 µg/mL and LOQ: 50 µg/mL), stability of solutions, and robustness.

In vivo effects of the alpha-synuclein misfolding inhibitor minzasolmin supports clinical development in Parkinson’s disease

Direct targeting of alpha-synuclein (ASYN) has emerged as a disease-modifying strategy for Parkinson’s disease and other synucleinopathies which is being approached using both small molecule compounds and ASYN-targeted biologics. Minzasolmin (UCB0599) is an orally bioavailable and brain-penetrant small molecule ASYN misfolding inhibitor in clinical development as a disease-modifying therapeutic for Parkinson’s disease. Herein the results of preclinical evaluations of minzasolmin that formed the basis for subsequent clinical development are described. Pharmacokinetic evaluations of intraperitoneal 1 and 5 mg/kg minzasolmin in wildtype mice revealed parallel and dose-proportional exposures in brain and plasma. Three-month administration studies in the Line 61 transgenic mouse model of PD were conducted to measure ASYN pathology and other PD-relevant endpoints including markers of CNS inflammation, striatal DAT labeling and gait. Reductions in ASYN pathology were correlated with improved aspects of gait and balance, reductions in CNS inflammation marker abundance, and normalized striatal DAT levels. These findings provide support for human dose determinations and have informed the translational strategy for clinical trial design and biomarker selection for the ongoing clinical studies of minzasolmin in patients living with early-stage Parkinson’s disease (ClinicalTrials.gov ID: NCT04658186; EudraCT Number 2020–003265).

Abstract LB301: Molecular pharmacology and broad synergy of the novel ATR inhibitor M1774 with DNA damaging anticancer agents

Abstract Ataxia telangiectasia and Rad3-related (ATR) checkpoint kinase orchestrates DNA damage response and repair pathways stimulated by replicative stresses. Recent studies have established that pharmacological inhibition of ATR is clinically promising. As M1774 is an oral ATR inhibitor in clinical development, we explored the molecular basis by which M1774 induces cancer cell death. As a single agent, we found that M1774 suppresses cancer cell viability at nanomolar concentrations with a potency higher than ceralasertib and berzosertib, but lower than gartisertib (M4344) and elimusertib in the small cell lung cancer (SCLC) cell lines H146, H82, and DMS114. We found that M1774 efficiently suppresses the ATR/CHK1 checkpoints. While M1774 alone induced apoptosis and G2/M cell cycle arrest at micromolar concentrations, at a non-toxic low dose, M1774 enhanced TOP1 inhibitor-mediated cancer cell death by preventing replication arrest and inducing DNA damage detected by EdU and γH2AX staining. Tandem mass tagging (TMT) coupled with mass spectrometry revealed that M1774 combined with SN-38 increases the expression of replication-related proteins (TIPIN, CDC45, TIMELESS, and RPA1) and G2/M-related proteins (PLK1 and CCNB1). To establish the synergistic combinations of M1774 with clinical anticancer DNA damaging agents in preclinical models, we performed experiments in cancer cell lines, patient-derived organoids, and xenograft models. Low doses of M1774 significantly synergized with the clinical TOP1 inhibitor SN-38, the TOP2 inhibitor etoposide, cisplatin, and the PARP inhibitor talazoparib in SCLC cell lines. We also found that M1774 significantly reversed chemoresistance to DNA-damaging agents in cancer cells lacking SLFN11 expression, suggesting that SLFN11 expression can be utilized for combination therapy with M1774 as a biomarker. The synergistic efficacy between M1774 and DNA-damaging agents was confirmed in SCLC patient-derived organoids, colon cancer patient-derived organoids, and H82 SCLC xenografts. Together, these results provide insights into the molecular mechanism and potential combination strategies for M1774 in cancer therapy. Citation Format: Ukhyun Jo, Yasuhiro Arakawa, Astrid Zimmermann, Daiki Taniyama, Makito Mizunuma, Lisa M Jenkins, Suresh Kumar, Frank T Zenke, Yves Pommier. Molecular pharmacology and broad synergy of the novel ATR inhibitor M1774 with DNA damaging anticancer agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB301.

Development, validation, and evaluation of a deep learning model to screen cyclin-dependent kinase 12 inhibitors in cancers

Deep learning-based in silico alternatives have been demonstrated to be of significant importance in the acceleration of the drug discovery process and enhancement of success rates. Cyclin-dependent kinase 12 (CDK12) is a transcription-related cyclin-dependent kinase that may act as a biomarker and therapeutic target for cancers. However, currently, there is no high selective CDK12 inhibitor in clinical development and the identification of new specific CDK12 inhibitors has become increasingly challenging due to their similarity with CDK13. In this study, we developed a virtual screening workflow that combines deep learning with virtual screening tools and can be applied rapidly to millions of molecules. We designed a Transformer architecture Drug-Target Interaction (DTI) model with dual-branched self-supervised pre-trained molecular graph models and protein sequence models. Our predictive model produced satisfactory predictions for various targets, including CDK12, with several novel hits. We screened a large compound library consisting of 4.5 million drug-like molecules and recommended a list of potential CDK12 inhibitors for further experimental testing. In kinase assay, compared to the positive CDK12 inhibitor THZ531, the compounds CICAMPA-01, 02, 03 displayed more effective inhibition of CDK12, up to three times as much as THZ531. The compounds CICAMPA-03, 05, 04, 07 showed less inhibition of CDK13 compare to THZ531. In vitro, the IC50 of CICAMPA-01, 04, 05, 06, 09 was less than 3 μM in the HER2 positive CDK12 amplification breast cancer cell line BT-474. Overall, this study provides a highly efficient and end-to-end deep learning protocol, in conjunction with molecular docking, for discovering CDK12 inhibitors in cancers. Additionally, we disclose five novel CDK12 inhibitors. These results may accelerate the discovery of novel chemical-class drugs for cancer treatment.

Structure of STAR-0215 Bound to Active Plasma Kallikrein Reveals a Novel Mechanism of Enzyme Inhibition

Inhibition of plasma kallikrein (pKal) activity is a validated mechanism for prevention of hereditary angioedema (HAE) attacks. High potency and long duration of action are key drivers of prophylactic efficacy of pKal inhibitors. STAR-0215 is a novel, potent and selective long-acting monoclonal antibody plasma kallikrein pKal inhibitor in clinical development. In monkeys dosed subcutaneously, STAR-0215 inhibits pKal activity rapidly and durably. We investigated STAR-0215 structure and binding to pKal and its inhibitory mechanism of action by utilizing Hydrogen/Deuterium Exchange Mass Spectrometry (HDX-MS) and Cryogenic Electron Microscopy (Cryo-EM).

Pharmacology of orismilast, a potent and selective PDE4 inhibitor.

There remains an unmet need for oral medications that are safe and efficacious for long-term management of chronic inflammatory skin diseases (CISD). Inhibition of phosphodiesterase 4 (PDE4) can modulate a broad range of pro-inflammatory cytokines that play a major role in CISD pathogenesis. Orismilast is a second generation PDE4 inhibitor in clinical development for CISD treatment. The objective of this study was to examine the PDE4 enzymatic activity and anti-inflammatory effects of orismilast in vitro, ex vivo, and in vivo. The PDE1-11 enzymatic activity of orismilast was tested in vitro using a single concentration of 308 nM orismilast. The PDE4 selectivity and inhibitory potency was further examined in a radiometric assay. Orismilast was tested on human whole blood and human peripheral blood mononuclear cells (PBMC) to determine effects on its cytokine secretion and inhibition profile ex vivo. Orismilast was orally administered in a murine model of chronic oxazolone-induced ear skin inflammation. Ear thickness, a marker of inflammation, and inflammatory cytokines were analysed. Orismilast selectively inhibited PDE4 and demonstrated potent inhibition of PDE4B and PDE4D subtype splice variants in vitro. Orismilast inhibited whole blood and PBMC production of tumour necrosis factor α (TNFα), and the secretion of T-helper (Th)1 (TNFα and IFNγ), Th17 (IL-22 and IL-23), and Th2 (IL-4, IL-5, and IL-13) related cytokines in PBMC. In vivo, 10 and 30 mg/kg doses of orismilast significantly reduced ear thickness and inflammation markers (p < 0.0001, respectively). Orismilast displayed selective and potent PDE4 inhibition and broad-spectrum anti-inflammatory activity in several pre-clinical models. The results of the study support clinical development of oral orismilast as a novel treatment option for CISD including psoriasis, atopic dermatitis, and hidradenitis suppurativa.

Effect of Food (Low and High Fat) on Pharmacokinetics of FCN-159, a Selective MEK Inhibitor, in Healthy Chinese Males.

FCN-159 is a novel, oral, potent, selective MEK1/2 inhibitor in clinical development for the treatment of NRAS-mutant advanced melanoma and neurofibromatosis type 1. We investigated the effect of food on the pharmacokinetics (PK), safety, and tolerability of FCN-159. In this single-center, open-label, phase 1 study with a three-period, three-sequence, crossover design, healthy Chinese male subjects (n = 24) were randomized (1:1:1) to receive a single, oral 8mg dose of FCN-159 in the fasted state (overnight, > 10h), and with a low-fat and a high-fat meal, separated by a 10-day washout. PK parameters including time to maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) were compared using geometric least-squares mean ratios (GLSMR), with the fasted state as the reference. A 90% CI for the GLSMR within 80-125% indicated no significant food effect. A low-fat meal (n = 23) did not affect the PK profile of FCN-159: G LSMR for AUC from time 0 to t (AUC0-t), 106.9% (90% CI 99.9-114.4%); AUC from time 0 to infinity (AUC0-∞), 106.8% (90% CI 100.0-114.0%); Cmax, 96.4% (90% CI 83.9-110.8%). A high-fat meal (n = 24) did not affect exposure to FCN-159 (GLSMR for AUC0-t, 99.4%; 90% CI 99.0-106.3%; AUC0-∞, 99.5 5%; 90% CI 93.2-106.1%), but modestly reduced Cmax by 15% (GLSMR 84.9%; 90% CI 74.0-97.3%). Both the low-fat and high-fat meals slightly prolonged the median time to Cmax by 0.5h (90% CI 0.5-1.0h). FCN-159 was generally well tolerated, with a lower incidence of treatment-emergent adverse events following administration in the fasted state than with a low-fat or high-fat meal (20.8%, 39.1%, and 37.5%, respectively). Food did not affect the PK profile of FCN-159 to a clinically meaningful extent compared with administration in the fasted state.

In Vitro Activity of Cefepime-Taniborbactam and Comparators against Clinical Isolates of Gram-Negative Bacilli from 2018 to 2020: Results from the Global Evaluation of Antimicrobial Resistance via Surveillance (GEARS) Program.

Taniborbactam is a novel cyclic boronate β-lactamase inhibitor in clinical development in combination with cefepime. We assessed the in vitro activity of cefepime-taniborbactam and comparators against a 2018-2020 collection of Enterobacterales (n = 13,731) and Pseudomonas aeruginosa (n = 4,619) isolates cultured from infected patients attending hospitals in 56 countries. MICs were determined by CLSI broth microdilution. Taniborbactam was tested at a fixed concentration of 4 μg/mL. Isolates with cefepime-taniborbactam MICs of ≥16 μg/mL underwent whole-genome sequencing. β-lactamase genes were identified in meropenem-resistant isolates by PCR/Sanger sequencing. Against Enterobacterales, taniborbactam reduced the cefepime MIC90 value by >64-fold (from >16 to 0.25 μg/mL). At ≤16 μg/mL, cefepime-taniborbactam inhibited 99.7% of all Enterobacterales isolates; >97% of isolates with multidrug-resistant (MDR) and ceftolozane-tazobactam-resistant phenotypes; ≥90% of isolates with meropenem-resistant, difficult-to-treat-resistant (DTR), meropenem-vaborbactam-resistant, and ceftazidime-avibactam-resistant phenotypes; 100% of VIM-positive, AmpC-positive, and KPC-positive isolates; 98.7% of extended-spectrum β-lactamase (ESBL)-positive; 98.8% of OXA-48-like-positive; and 84.6% of NDM-positive isolates. Against P. aeruginosa, taniborbactam reduced the cefepime MIC90 value by 4-fold (from 32 to 8 μg/mL). At ≤16 μg/mL, cefepime-taniborbactam inhibited 97.4% of all P. aeruginosa isolates; ≥85% of isolates with meropenem-resistant, MDR, and meropenem-vaborbactam-resistant phenotypes; >75% of isolates with DTR, ceftazidime-avibactam-resistant, and ceftolozane-tazobactam-resistant phenotypes; and 87.4% of VIM-positive isolates. Multiple potential mechanisms, including carriage of IMP, certain alterations in PBP3, permeability (porin) defects, and possibly, upregulation of efflux were present in most isolates with cefepime-taniborbactam MICs of ≥16 μg/mL. We conclude that cefepime-taniborbactam exhibited potent in vitro activity against Enterobacterales and P. aeruginosa and inhibited most carbapenem-resistant isolates, including those carrying serine carbapenemases or NDM/VIM metallo-β-lactamases (MBLs).

A Phase 1/2 Multi-Center, Dose-Finding Study to Assess Safety, Tolerability, PK and Efficacy of ZN-d5, a Novel BCL-2 Inhibitor, for Treatment of Subjects with Relapsed/Refractory AL Amyloidosis

Background: Light-chain (AL) amyloidosis arises from a plasma cell clone that overproduces immunoglobulin light chains which aggregate and deposit within tissues and organs, interfering with normal function. Commonly, cardiac, hepatic, and renal involvement produce the major morbidities observed in this rare disease. At present, treatment of AL amyloidosis aims at the elimination of the plasma cell clone to rapidly reduce the level of circulating light chains. Recently, the addition of subcutaneous daratumumab to the standard CyBorD (cyclophosphamide, bortezomib, and dexamethasone) as first-line regimen, was shown to significantly improve complete hematologic and organ response rates. However, the management of patients with relapsed or refractory disease remains challenging. Pre-clinical and clinical data have shown that BCL-2 inhibition is active against malignant plasma cells, and may be particularly effective against cells harboring the t(11;14) translocation, found in about half of AL amyloidosis patients. Interestingly, small, retrospective studies have shown that BCL-2 inhibition may be an effective treatment option for patients with AL amyloidosis, particularly those with t(11;14). ZN-d5 is a novel, highly BCL-2-selective BCL-2 inhibitor in clinical development for hematologic malignancies, which is active against multiple myeloma in preclinical models, and which may be useful in the treatment of AL amyloidosis. Methods: ZN-d5-003 is a multicenter, international Phase 1/2 clinical trial evaluating single-agent oral ZN-d5 in relapsed or refractory AL amyloidosis subjects. In the Phase 1 part, the primary objectives are to determine the safety, tolerability and maximum tolerated dose of ZN-d5, and to determine the recommended Phase 2 dose. Cohorts of increasing doses (200mg; 400mg; 800mg; 1200mg; 1600mg QD) will enroll subjects based on Bayesian Optimum Interval (BOIN) design. In Phase 2, the primary objective is to assess the hematological response rate (HRR) among subjects with or without t(11;14) translocation. Bayesian Optimal Phase 2 (BOP2) design is implemented for interim efficacy monitoring. Key criteria for eligibility include the following: subjects must have a biopsy-confirmed diagnosis of AL amyloidosis, at least 1 and no more than 3 prior lines of therapy (including HSCT), adequate organ function and ECOG performance status of 0-2. All subjects must have measurable disease defined as dFLC of at least 20 mg/L; those considered for the trial will undergo bone marrow aspiration for assessment of t(11;14) status by FISH. Both t(11;14)-positive and -negative subjects are eligible for the study, however they will be separately analyzed for safety and efficacy. Subjects must have a history of organ involvement (current measurable organ disease is not required). Exclusion criteria include non-AL amyloidosis, diagnosis of multiple myeloma per 2014 IMWG criteria, or Mayo 2012 Stage IV disease. The study is expected to enroll up to approximately 140 subject at approximately 25 sites for phase 1, and at least 50 sites for phase 2. Conclusion: This study will evaluate treatment of AL amyloidosis utilizing BCL-2 inhibition and will test the hypothesis of whether t(11;14) is a relevant predictive biomarker. Dose escalation cohorts are currently undergoing evaluation and the study is open to enrollment. Upon determination of a recommended phase 2 dose, the study will commence Phase 2. Clinical trial: NCT05199337.

Clinical activity of 9-ING-41, a small molecule selective glycogen synthase kinase-3 beta (GSK-3β) inhibitor, in refractory adult T-Cell leukemia/lymphoma

ABSTRACT GSK-3β is a serine/threonine kinase implicated in tumorigenesis and chemotherapy resistance. GSK-3β blockade downregulates the NF-κB pathway, modulates immune cell PD-1 and tumor cell PD-L1 expression, and increases CD8 + T cell and NK cell function. We report a case of adult T-cell leukemia/lymphoma (ATLL) treated with 9-ING-41, a selective GSK-3β inhibitor in clinical development, who achieved a durable response. A 43-year-old male developed diffuse lymphadenopathy, and biopsy of axillary lymph node showed acute-type ATLL. Peripheral blood flow cytometry revealed a circulating clonal T cell population, and CSF was positive for ATLL involvement. After disease progression on the 3rd line of treatment, he started treatment with 9-ING-41 monotherapy in a clinical trial (NCT03678883). CT imaging after seven months showed a partial response. Sustained reduction of peripheral blood ATLL cells lasted 15 months. Treatment of patient-derived CD8 + T cells with 9-ING-41 increased the secretion of IFN-γ, granzyme B, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In conclusion, treatment of a patient with refractory ATLL with the GSK-3β inhibitor 9-ING-41 resulted in a prolonged response. Ongoing experiments are investigating the hypothesis that 9-ING-41-induced T cell activation and immunomodulation contributes to its clinical activity. Further clinical investigation of 9-ING-41 for treatment of ATLL is warranted.

Abstract 6219: WM-S1, the novel small molecule inhibitor of mutant RTK/receptor tyrosine kinase, for the treatment of cancer

Abstract As the representative targeted anticancer drug for colon cancer patients, cetuximab is the EGFR targeted therapeutic antibody and used for treatment of KRAS wild type cancers. Even some patient with KRAS wt gene did not respond cetuximab. However, there is no treatment available for cetuximab-resistant patient group, which is almost 50% of KRAS WT gene holders. Recently, our team identified cetuximab primary resistant related proteins named as mtRTK (mutant receptor tyrosine kinase) by array analysis based cetuximab responder or non-responder colon cancer patient tissues. We investigated mtRTK’s oncogenic potential as a novel anti-cancer target. A large proportion of colon cancer patients (36.2% Caucasian, 56.9% Korean) expressed the mtRTK was identified, using the sequencing analysis of patient samples. Based on these results, our efforts have led to the discovery of WM-S1, mtRTK inhibitor, which is the first mtRTK inhibitor in clinical development. The potent enzyme inhibitor showed a high anticancer activity confirmed in Patient-Derived Cells (PDC) and Patient-Derived Xenograft (PDX) animal models expressing the mutation. In preclinical studies demonstrate that WM-S1 is well tolerated in rats and dogs. Furthermore, WM-S1 has potent anticancer activities for various solid tumor (NSCLC, cholangiocarcinoma, etc.) including activated mtKRAS colon cancer expressing the mtRTK. Currently we are investigating WM-S1 in a phase 1a trial in AUS, which is the first mtRTK inhibitor in clinical development. Meanwhile, the mtRTK inhibitor WM-S1 drives antitumor immunity (with anti-PD-L1) in NSCLC. Combinational approaches with immunotherapy showed that synergistic effect of WM-S1 and anti-PD1 monoclonal antibody, suppressing tumor growth by 75% in anti-PD1 resistance NSCLC-derived humanized mouse model. A phase 1b trial is expected to develop WM-S1 through not only indication expansion but also combination therapy with immuno-checkpoint inhibitors in the USA, AUS and KOR from Q2 2022. In conclusion, mtRTK is a potential oncogenic driver mutation in various solid tumor. A first-in-class anticancer agent WM-S1 targeting mtRTK can be promising therapeutic agents for cetuximab-resistant colon cancer patients regardless of KRAS mutation status and other cancers. Citation Format: Joseph Kim, Jai-Hee Moon, Kyung-Mi Lee, Hyun Ryu, Eun Hye Park, Sang Hee Kim, Jeong Seok Kim, Young Ok Ko, Yong Seok Kim, Hyo Jin Kim, Tae Young Kim Kim, Moon Seong Yoo, Soll Jin, Seongrak Kim, Yoon Sun Park, Min Ki Lee, Mi So Lee, Ji Hyun Go, Yu Geun Ji, Jun Hyung Lee, Haneul Lee, Min Hwa Kim, Eun Hee Ko, Yeo Jin Lee, Seung-Mi Kim, Joon-yee Jeong, Yeon-seoung Choi, Seung-geon Bae, Jinwoo Lee, Won Jun Lee, Min-Kyeong Kim, Ji min Shin, Dong-in Koh, Sun-Chul Hur, Chun-Ho Park, Hyun Ho Lee, Dong-Hoon Jin. WM-S1, the novel small molecule inhibitor of mutant RTK/receptor tyrosine kinase, for the treatment of cancer [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 6219.

Abstract 1064: Targeting stromal autotaxin synergizes with TGF beta inhibition in pancreatic cancer

Abstract The TGFβ receptor inhibitor galunisertib (GAL) has been demonstrated as an effective strategy for the treatment of pancreatic cancer (PC) patients, in part through the modulation of stromal microenvironment. However, alternative pathways driving stromal paracrine signals might impair its effect. Autotaxin (ATX) is an enzyme that converts lysophosphatidylcholine into its bioactive lipid, lysophosphatidic acid (LPA), which in turn promotes inflammation and fibrosis, and contributes to treatment resistance. IOA-289 is a novel ATX inhibitor in clinical development for the treatment of tumors burdened with a high degree of stromal involvement. Here, we hypothesized that ATX could sustain an adaptive response upon inhibition of TGFβ receptor signaling, impairing GAL antitumor activity.Among ten different murine PC orthotopic models, mice bearing RC416 tumors had the highest plasma levels of TGFβ1 as well as high infiltration of cancer associated fibroblasts (CAFs) and fibrosis as measured by Masson’s staining. In coculture models of RC416 with murine pancreatic stellate cells (mPSC4), we measured a significant overexpression of ATX upon treatment with galunisertib mainly by mPSC4, which showed a skewing toward an inflammatory iCAF phenotype through the upregulation of CXCL1 and LY6C1 and the down-regulation of myCAF markers including ACTA2 and Taglin. In the RC416-mPSC4 coculture model, anti-tumor activity was achieved with a combination of gemcitabine plus GAL plus IOA-289, whereas these treatments were ineffective in single culture conditions. Mice bearing RC416 tumors reached a statistically significantly longer survival following treatment with gemcitabine plus IOA-289 or gemcitabine plus GAL [median overall survival (mOS)= 35 days, p&amp;lt;0.05] compared with any single treatment or no treatment control. Most importantly, mice treated with the triple combination of gemcitabine plus IOA-289 and galunisertib had a significantly longer survival than any double combination treatments [mOS=47 days, p&amp;lt;0.05]. In mice treated with gemcitabine in combination with IOA-289 and/or GAL we measured a significantly reduced infiltration of CAFs, a reduction in plasma levels of CTGF and a diminished degree of fibrosis compared with any single control treatment.In conclusion, we demonstrate that the overexpression of autotaxin by stromal PSC might be an adaptive mechanism in response to TGFβ receptor inhibition. IOA-289 is a novel agent that warrants further clinical development in combination with gemcitabine plus GAL for the treatment of PC patients. Citation Format: Fabio Sabbadini, Monica Bertolini, Domenico Mangiameli, Serena Contarelli, Zoë Johnson, Michael M. Lahn, Silvia Pietrobono, Davide Melisi. Targeting stromal autotaxin synergizes with TGF beta inhibition in pancreatic cancer [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 1064.

Abstract 5496: Efficacy and immune profiling of PI3K delta inhibitor zandelisib (ME-401) in a preclinical chronic lymphocytic leukemia (CLL) model

Abstract Phosphatidylinositol-3 kinase (PI3K) delta signaling is essential for CLL B cell survival and proliferation. Several PI3K inhibitors are approved for treatment of CLL, but PI3K inhibitor-induced alterations in T cell function have been correlated with immune-related adverse events (irAEs). Zandelisib is a novel selective PI3Kδ inhibitor in clinical development with an intermittent dosing schedule for treatment of B cell malignancies. Here, we investigated the dynamic immunomodulatory properties of zandelisib alone or in combination with BTK inhibitor ibrutinib in normal human T cells, as well as the impact of continuous dosing of zandelisib on effector and regulatory immune cells, irAEs, and survival in a preclinical CLL murine model. Normal human T cells treated ex vivo with zandelisib, ibrutinib, or both were assessed for phenotype and function. A CLL model was initiated by transferring leukemic EμTCL1 splenocytes into syngeneic wildtype recipients. CLL-bearing mice were treated with vehicle or zandelisib (50 mpk bid or 100 mpk qd) for 3 weeks (n=5 per group). Antitumor efficacy, T cell and myeloid subsets in blood, bone marrow and spleen were analyzed. Survival was also observed in a separate cohort of mice treated with zandelisib (100 mpk qd). T cell proliferation was impaired by zandelisib (250nM) and ibrutinib (100 nM) alone, with the combination further reducing T cell proliferation. Zandelisib decreased expression of suppressive markers PD-1, CTLA-4, GITR and CD39 on iTregs; however, no further decrease was observed when zandelisib was combined with ibrutinib. Zandelisib also reduced normal T cell activation and expression of immune checkpoints PD-1 and CTLA-4 on CD4+ T cells and dose dependently inhibited T cell memory differentiation ex vivo, increasing the naïve/central to effector memory ratio. Combination with ibrutinib did not further affect T cell activation, checkpoint expression or memory differentiation. In the CLL murine model, no meaningful difference was seen between bid or qd administration of zandelisib in the reduction of tumor burden (CD19+ CD5+ CLL cells). Zandelisib treatment reduced activated T cells, antigen-experienced T cells, and Tregs. Increased naïve/central to effector memory ratio was observed in treated mice, and PD-1 was downregulated on memory T cells, indicating less T cell exhaustion. Zandelisib decreased macrophages in the spleen but did not impact myeloid-derived suppressor cells. Zandelisib treatment improved survival of CLL-bearing mice significantly when compared to vehicle group (median survival of zandelisib group 140 days vs. 105 days vehicle). In conclusion, zandelisib treatment reduced Tregs, prevented terminal memory differentiation, and T-cell exhaustion—features that have been shown to permit CLL immune evasion—demonstrated antitumor efficacy, and improved overall survival in a preclinical CLL model. Citation Format: Kamira Maharaj, Melanie Mediavilla-Varela, John J. Powers, Sandra Wiley, Angimar Uriepero, Wael Gamal, Kun Jiang, Eva Sahakian, Javier Pinilla-Ibarz. Efficacy and immune profiling of PI3K delta inhibitor zandelisib (ME-401) in a preclinical chronic lymphocytic leukemia (CLL) model [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 5496.

Inhaled seralutinib exhibits potent efficacy in models of pulmonary arterial hypertension.

Signalling through platelet-derived growth factor receptor (PDGFR), colony-stimulating factor 1 receptor (CSF1R) and mast/stem cell growth factor receptor kit (c-KIT) plays a critical role in pulmonary arterial hypertension (PAH). We examined the preclinical efficacy of inhaled seralutinib, a unique small-molecule PDGFR/CSF1R/c-KIT kinase inhibitor in clinical development for PAH, in comparison to a proof-of-concept kinase inhibitor, imatinib. Seralutinib and imatinib potency and selectivity were compared. Inhaled seralutinib pharmacokinetics/pharmacodynamics were studied in healthy rats. Efficacy was evaluated in two rat models of PAH: SU5416/Hypoxia (SU5416/H) and monocrotaline pneumonectomy (MCTPN). Effects on inflammatory/cytokine signalling were examined. PDGFR, CSF1R and c-KIT immunohistochemistry in rat and human PAH lung samples and microRNA (miRNA) analysis in the SU5416/H model were performed. Seralutinib potently inhibited PDGFRα/β, CSF1R and c-KIT. Inhaled seralutinib demonstrated dose-dependent inhibition of lung PDGFR and c-KIT signalling and increased bone morphogenetic protein receptor type 2 (BMPR2). Seralutinib improved cardiopulmonary haemodynamic parameters and reduced small pulmonary artery muscularisation and right ventricle hypertrophy in both models. In the SU5416/H model, seralutinib improved cardiopulmonary haemodynamic parameters, restored lung BMPR2 protein levels and decreased N-terminal pro-brain natriuretic peptide (NT-proBNP), more than imatinib. Quantitative immunohistochemistry in human lung PAH samples demonstrated increased PDGFR, CSF1R and c-KIT. miRNA analysis revealed candidates that could mediate seralutinib effects on BMPR2. Inhaled seralutinib was an effective treatment of severe PAH in two animal models, with improved cardiopulmonary haemodynamic parameters, a reduction in NT-proBNP, reverse remodelling of pulmonary vascular pathology and improvement in inflammatory biomarkers. Seralutinib showed greater efficacy compared to imatinib in a preclinical study.

Dual BTK/SYK inhibition with CG-806 (luxeptinib) disrupts B-cell receptor and Bcl-2 signaling networks in mantle cell lymphoma

Aberrant B-cell receptor (BCR) signaling is a key driver in lymphoid malignancies. Bruton tyrosine kinase (BTK) inhibitors that disrupt BCR signaling have received regulatory approvals in therapy of mantle cell lymphoma (MCL). However, responses are incomplete and patients who experience BTK inhibitor therapy failure have dire outcomes. CG-806 (luxeptinib) is a dual BTK/SYK inhibitor in clinical development in hematologic malignancies. Here we investigated the pre-clinical activity of CG-806 in MCL. In vitro treatment with CG-806 thwarted survival of MCL cell lines and patient-derived MCL cells in a dose-dependent manner. CG-806 blocked BTK and SYK activation and abrogated BCR signaling. Contrary to ibrutinib, CG-806 downmodulated the anti-apoptotic proteins Mcl-1 and Bcl-xL, abrogated survival of ibrutinib-resistant MCL cell lines, and partially reversed the pro-survival effects of stromal microenvironment-mimicking conditions in primary MCL cells. Dual BTK/SYK inhibition led to mitochondrial membrane depolarization accompanied by mitophagy and metabolic reprogramming toward glycolysis. In vivo studies of CG-806 demonstrated improved survival in one of the two tested aggressive MCL PDX models. While suppression of the anti-apoptotic Bcl-2 family proteins and NFκB signaling correlated with in vivo drug sensitivity, OxPhos and MYC transcriptional programs were upregulated in the resistant model following treatment with CG-806. BAX and NFKBIA were implicated in susceptibility to CG-806 in a whole-genome CRISPR-Cas9 library screen (in a diffuse large B-cell lymphoma cell line). A high-throughput in vitro functional drug screen demonstrated synergy between CG-806 and Bcl-2 inhibitors. In sum, dual BTK/SYK inhibitor CG-806 disrupts BCR signaling and induces metabolic reprogramming and apoptosis in MCL. The Bcl-2 network is a key mediator of sensitivity to CG-806 and combined targeting of Bcl-2 demonstrates synergy with CG-806 warranting continued exploration in lymphoid malignancies.

Induction of senescence-associated secretory phenotype underlies the therapeutic efficacy of PRC2 inhibition in cancer

The methyltransferase Polycomb Repressive Complex 2 (PRC2), composed of EZH2, SUZ12, and EED subunits, is associated with transcriptional repression via tri-methylation of histone H3 on lysine 27 residue (H3K27me3). PRC2 is a valid drug target, as the EZH2 gain-of-function mutations identified in patient samples drive tumorigenesis. PRC2 inhibitors have been discovered and demonstrated anti-cancer efficacy in clinic. However, their pharmacological mechanisms are poorly understood. MAK683 is a potent EED inhibitor in clinical development. Focusing on MAK683-sensitive tumors with SMARCB1 or ARID1A loss, we identified a group of PRC2 target genes with high H3K27me3 signal through epigenomic and transcriptomic analysis. Multiple senescence-associated secretory phenotype (SASP) genes, such as GATA4, MMP2/10, ITGA2 and GBP1, are in this group besides previously identified CDKN2A/p16. Upon PRC2 inhibition, the de-repression of SASP genes is detected in multiple sensitive models and contributes to decreased Ki67+, extracellular matrix (ECM) reorganization, senescence associated inflammation and tumor regression even in CDKN2A/p16 knockout tumor. And the combination of PRC2 inhibitor and CDK4/6 inhibitor leads to better effect. The genes potential regulated by PRC2 in neuroblastoma samples exhibited significant enrichment of ECM and senescence associated inflammation, supporting the clinical relevance of our results. Altogether, our results unravel the pharmacological mechanism of PRC2 inhibitors and propose a combination strategy for MAK683 and other PRC2 drugs.

73. Interim Resistance Analysis of Long-Acting Lenacapavir in Treatment-Naïve People with HIV at 28 Weeks

BackgroundLenacapavir (LEN) is a first-in-class HIV-1 capsid (CA) inhibitor in clinical development for treatment and prevention of HIV-1 infection. CALIBRATE is an ongoing, phase 2 clinical study evaluating subcutaneous (SC) or oral LEN, in combination with other antiretrovirals, in treatment-naïve people with HIV-1. High rates of virologic success (HIV-1 RNA < 50 copies/mL) were achieved with LEN-based regimens by FDA Snapshot analysis at Week 28. Here, we present interim resistance analyses through Week 28. MethodsParticipants were randomized (2:2:2:1) to treatment groups (TG) (Figure): SC LEN + oral daily emtricitabine/tenofovir alafenamide (F/TAF); at Week 28, participants switch F/TAF to oral TAF (TG-A) or bictegravir (B, BIC) (TG-B); oral daily LEN + F/TAF (TG-C), or oral daily B/F/TAF (TG-D). Genotypic analyses (population sequencing) of HIV-1 reverse transcriptase and integrase, and genotypic (deep sequencing)/phenotypic analyses for CA were performed at screening; genotypic and phenotypic analyses were conducted at confirmed virologic failure. FigureCALIBRATE Study Design Results182 participants were randomized and dosed in TG-A to D (n=52, 53, 52, 25). Most participants had subtype B HIV-1 (92.9%). Sequence analysis of baseline samples found 65% of amino acid residues were conserved with < 1% variation across CA overall, and 55% of residues were fully conserved. No mutations were detected at 6 positions in CA associated with reduced susceptibility to LEN in vitro; residues were fully conserved at 5 positions (L56, M66, Q67, K70, N74), and < 2% variation was observed at 1 position (T107). Three participants met the criteria for resistance analysis: 2 participants resuppressed to < 50 copies/mL while continuing treatment. One participant on SC LEN + F/TAF developed emergent resistance to LEN (Q67H+K70R) and emtricitabine (M184M/I), followed by resuppression after starting dolutegravir, zidovudine + lamivudine, tenofovir disoproxil fumarate. ConclusionEmergent resistance to LEN was uncommon in treatment-naïve participants receiving SC or oral LEN (0.6%, 1/157). These interim resistance findings support the ongoing evaluation of LEN for treatment and prevention of HIV.Disclosures Laurie VanderVeen, PhD, Gilead Sciences (Employee, Shareholder) Nicolas Margot, MA, Gilead Sciences (Employee, Shareholder) Vidula Naik, MSc, Gilead Sciences (Employee, Shareholder) Silvia Chang, Masters, Gilead Sciences, Inc (Employee, Shareholder) Ross Martin, PhD, Gilead Sciences, Inc (Employee, Shareholder) Hadas Dvory-Sobol, PhD, Gilead Sciences (Employee, Shareholder) Martin Rhee, MD, Gilead Sciences (Employee, Shareholder) Christian Callebaut, PhD, Gilead Sciences (Employee, Shareholder)