Selective Kinase Inhibitor Research Articles

The SRC family kinase inhibitor NXP900 demonstrates potent antitumor activity in squamous cell carcinomas

NXP900 is a selective and potent SRC family kinase (SFK) inhibitor, currently being dosed in a phase 1 clinical trial, that locks SRC in the “closed” conformation, thereby inhibiting both kinase-dependent catalytic activity and kinase-independent functions. In contrast, several multi-targeted kinase inhibitors that inhibit SRC, including dasatinib and bosutinib, bind their target in the active “open” conformation, allowing SRC and other SFKs to act as a scaffold to promote tumorigenesis through non-catalytic functions. NXP900 exhibits a unique target selectivity profile with sub-nanomolar activity against SFK members over other kinases. This results in highly potent and specific SFK pathway inhibition. Here, we demonstrate that esophageal squamous cell carcinomas (ESCC) and head and neck squamous cell carcinomas (HNSCC) are exquisitely sensitive to NXP900 treatment in cell culture and in vivo, and we identify a patient population that could benefit from treatment with NXP900.

Combined inhibition of KRASG12C and mTORC1 kinase is synergistic in non-small cell lung cancer

Current KRASG12C (OFF) inhibitors that target inactive GDP-bound KRASG12C cause responses in less than half of patients and these responses are not durable. A class of RASG12C (ON) inhibitors that targets active GTP-bound KRASG12C blocks ERK signaling more potently than the inactive-state inhibitors. Sensitivity to either class of agents is strongly correlated with inhibition of mTORC1 activity. We have previously shown that PI3K/mTOR and ERK-signaling pathways converge on key cellular processes and that inhibition of both pathways is required for inhibition of these processes and for significant antitumor activity. We find here that the combination of a KRASG12C inhibitor with a selective mTORC1 kinase inhibitor causes synergistic inhibition of Cyclin D1 expression and cap-dependent translation. Moreover, BIM upregulation by KRASG12C inhibition and inhibition of MCL-1 expression by the mTORC1 inhibitor are both required to induce significant cell death. In vivo, this combination causes deep, durable tumor regressions and is well tolerated. This study suggests that the ERK and PI3K/mTOR pathways each mitigate the effects of inhibition of the other and that combinatorial inhibition is a potential strategy for treating KRASG12C-dependent lung cancer.

7-Amino-3-phenyl-2-methyl-pyrazolopyrimidine derivatives inhibit human rhinovirus replication

Small molecules that exhibit broad-spectrum enteroviral inhibitory activity by targeting viral replication proteins are highly desired in antiviral drug discovery studies. To discover new human rhinovirus (hRV) inhibitors, we performed a high-throughput screening of 100,000 compounds from the Korea Chemical Bank library. This search led to identification of two phosphatidylinositol-4-kinase IIIβ (PI4KIIIβ) inhibitors having the pyrazolo-pyrimidine core structure, which display moderate anti-rhinoviral activity along with mild cytotoxicity. The results of a study aimed at optimizing the activity of the hit compounds showed that the pyrazolo-pyrimidine derivative 6f exhibits the highest activity (EC50 = 0.044, 0.066, and 0.083 μM for hRV-B14, hRV-A16, and hRV-A21, respectively) and moderate toxicity (CC50 = 31.38 μM). Furthermore, 6f has broad-spectrum activities against various hRVs, coxsackieviruses and other enteroviruses, such as EV-A71, EV-D68. An assessment of kinase inhibition potencies demonstrated that 6f possesses a high and selective kinase inhibition activity against PI4KIIIβ (IC50 value of 0.057 μM) and not against PI4KIIIα (>10 μM). Moreover, 6f exhibits modest hepatic stability (46.9 and 55.3 % remaining after 30 min in mouse and human liver microsomes, respectively). Finally, an in vivo study demonstrated that 6f possesses a desirable pharmacokinetic profile reflected in low systemic clearance (0.48 L∙h−1 kg−1) and modest oral bioavailability (52.4 %). Hence, 6f (KR-26549) appears to be an ideal lead for the development of new antiviral drugs.

Identification of 6-Anilino Imidazo[4,5-c]pyridin-2-ones as Selective DNA-Dependent Protein Kinase Inhibitors and Their Application as Radiosensitizers.

The dominant role of non-homologous end-joining in the repair of radiation-induced double-strand breaks identifies DNA-dependent protein kinase (DNA-PK) as an excellent target for the development of radiosensitizers. We report the discovery of a new class of imidazo[4,5-c]pyridine-2-one DNA-PK inhibitors. Structure-activity studies culminated in the identification of 78 as a nM DNA-PK inhibitor with excellent selectivity for DNA-PK compared to related phosphoinositide 3-kinase (PI3K) and PI3K-like kinase (PIKK) families and the broader kinome, and displayed DNA-PK-dependent radiosensitization of HAP1 cells. Compound 78 demonstrated robust radiosensitization of a broad range of cancer cells in vitro, displayed high oral bioavailability, and sensitized colorectal carcinoma (HCT116/54C) and head and neck squamous cell carcinoma (UT-SCC-74B) tumor xenografts to radiation. Compound 78 also provided substantial tumor growth inhibition of HCT116/54C tumor xenografts in combination with radiation. Compound 78 represents a new, potent, and selective class of DNA-PK inhibitors with significant potential as radiosensitizers for cancer treatment.

Pharmacokinetics and Exposure-Response Analyses to Support Dose Selection of Upadacitinib in Crohn's Disease.

Upadacitinib, a selective Janus kinase inhibitor, is the first orally administered therapy approved for the treatment of Crohn's disease (CD). This work characterized the pharmacokinetics of upadacitinib in CD patients and evaluated the relationships between upadacitinib steady-state plasma exposures and efficacy as well as safety parameters during the 12-week induction and the 52-week maintenance periods, to provide dosing recommendations for the treatment of CD. Upadacitinib pharmacokinetics in CD patients administered the extended-release formulation were consistent with patient populations in other approved indications. None of the evaluated CD-specific patient characteristics (e.g., disease location and prior gastrointestinal surgeries) had a meaningful impact on upadacitinib pharmacokinetics. Exposure-response analyses during 12-week induction treatment showed that response across all evaluated efficacy end points were approaching a plateau at median plasma exposures associated with 45 mg QD. Analyses for the maintenance period demonstrated that 30 mg QD is predicted to provide an additional 8% to 10% benefit for endoscopic response and endoscopic remission compared with 15 mg QD in patients who failed biologics. The analyses for safety showed a statistically significant relationship between increasing upadacitinib plasma exposures and the percentage of patients experiencing >2 g/dL decrease in hemoglobin from Baseline during induction and showed shallow relationships for serious infections and herpes zoster during the maintenance period. These results demonstrated adequate absorption of the extended-release formulation of upadacitinib in CD patients. The exposure-response analyses confirmed that 45 mg QD dose maximized efficacy as induction treatment and supported the selection of 15 mg QD or 30 mg QD as the maintenance doses.

PI3K PROTAC overcomes the lapatinib resistance in PIK3CA-mutant HER2 positive breast cancer

Although anti-HER2 therapy has made significant strides in reducing metastasis and relapse in HER2-positive breast cancer, resistance to agents like trastuzumab, pertuzumab, and lapatinib frequently develops in patients undergoing treatment. Previous studies suggest that the hyperactivation of the PI3K-AKT signaling pathway by PIK3CA/PTEN gene mutations is implicated in HER2 resistance. In this study, we introduce a novel PI3K-p110α Proteolysis TAargeting Chimera (PROTAC) that effectively inhibits the proliferation of breast cancer cells by degrading PI3K-p110α. When tested in two lapatinib-resistant cell lines, JIMT1 and MDA-MB-453, both of which harbor PIK3CA mutations, the PI3K PROTAC notably reduced cell proliferation and induced G1 phase cell cycle arrest. Importantly, even at very low concentrations, PI3K PROTAC restored sensitivity to lapatinib. Furthermore, the efficacy of PI3K PROTAC surpassed that of Alpelisib, a selective PI3K-p110α kinase inhibitor in clinic. The superior performance of PI3K PROTAC was also confirmed in lapatinib-resistant breast cancer xenograft tumors and patient-derived breast cancer organoids (PDOs). In conclusion, this study reveals that the novel PI3K PROTAC we synthesized could serve as an effective agent to overcome lapatinib resistance.

Pharmacological inhibition of CDK4/6 impairs diffuse pleural mesothelioma 3D spheroid growth and reduces viability of cisplatin-resistant cells.

Diffuse pleural mesothelioma (DPM) of the pleura is a highly aggressive and treatment-resistant cancer linked to asbestos exposure. Despite multimodal treatment, the prognosis for DPM patients remains very poor, with an average survival of 2 years from diagnosis. Cisplatin, a platinum-based chemotherapy drug, is commonly used in the treatment of DPM. However, the development of resistance to cisplatin significantly limits its effectiveness, highlighting the urgent need for alternative therapeutic strategies. New selective inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) have shown promise in various malignancies by inhibiting cell cycle progression and suppressing tumor growth. Recent studies have indicated the potential of abemaciclib for DPM therapy, and a phase II clinical trial has shown preliminary encouraging results. Here, we tested abemaciclib, palbociclib, and ribociclib on a panel of DPM cell lines and non-tumor mesothelial(MET-5A) cells. Specifically, we focused on abemaciclib, which was the mosteffective cytotoxic agent on all the DPM cell lines tested. Abemaciclib reduced DPM cell viability, clonogenic potential, and ability to grow as three-dimensional (3D) spheroids. In addition, abemaciclib induced prolonged effects, thereby impairing second-generation sphere formation and inducing G0/G1 arrest and apoptosis/ necrosis. Interestingly, single silencing of RB family members did not impair cell response to abemaciclib, suggesting that they likely complement each other in triggering abemaciclib's cytostatic effect. Interestingly, abemaciclib reduced the phosphorylation of AKT, which is hyperactive in DPM and synergized with the pharmacological AKT inhibitor (AKTi VIII). Abemaciclib also synergized with cisplatin and reduced the viability of DPM cells with acquired resistance to cisplatin. Overall, our results suggest that CDK4/6 inhibitors alone or in combination with standard of care should be further explored for DPM therapy.

A phase I randomized study to evaluate safety, pharmacokinetics, and pharmacodynamics of SIR2446M, a selective RIPK1 inhibitor, in healthy participants.

Activation of receptor-interacting protein kinase 1 (RIPK1), a broadly expressed serine/threonine protein kinase, by pro-inflammatory cytokines and pathogens can result in apoptosis, necroptosis, or inflammation. RIPK1 inhibition has been shown to reduce inflammation and cell damage in preclinical studies and may have therapeutic potential for degenerative and inflammatory diseases. SIR2446 is a potent and selective novel small molecule RIPK1 kinase inhibitor. This phase I, randomized, double-blind, placebo-controlled study in Australia (ACTRN12621001621808) evaluated the safety (primary objective), pharmacokinetics, and pharmacodynamics of single (3-600 mg) and multiple (5-400 mg for 10 days) ascending oral doses of SIR2446M (SIR2446 magnesium salt form) in healthy adults from Nov 24, 2021, until May 01, 2023. All treatment-emergent adverse events (TEAEs) were mild/moderate. The most reported TEAEs were vascular access site pain, headache, and rash morbilliform. SIR2446M plasma half-lives ranged from 11 to 19 h and there were no major deviations from dose proportionality for maximum concentration and area under the curve across doses. Renal excretion of unchanged SIR2446 was minimal. No marked accumulation was observed (mean accumulation ratio, 1.2-1.6) after multiple daily doses. A high-fat meal mildly reduced the exposure but was not considered clinically significant. SIR2446M had a rapid and sustained inhibitory effect on the activity of RIPK1, with an overall 90% target engagement at repeated doses ranging from 30 to 400 mg in peripheral blood mononuclear cells exvivo stimulated to undergo necroptosis. The favorable safety, pharmacokinetic, and pharmacodynamic profile of SIR2446M in healthy participants supports its further clinical development in patients with degenerative and inflammatory diseases.

Efficacy and safety of deuruxolitinib, an oral selective Janus kinase inhibitor, in adults with alopecia areata: Results from the Phase 3 randomized, controlled trial (THRIVE-AA1)

BackgroundAlopecia areata (AA) is a hair loss disorder that can seriously impact quality of life. Janus kinase (JAK) inhibitors, including deuruxolitinib, have previously demonstrated significant hair regrowth in AA. ObjectiveThe Phase 3 THRIVE-AA1 randomized, double-blinded, placebo-controlled trial (NCT04518995) evaluated safety and efficacy of the oral JAK1/JAK2 inhibitor deuruxolitinib in adult patients with AA. MethodsPatients aged 18–65 years with ≥50% hair loss were randomized to deuruxolitinib 8 mg BID, deuruxolitinib 12 mg BID, or placebo for 24 weeks. The primary endpoint was percentage of patients achieving Severity of Alopecia Tool (SALT) score ≤20. A key secondary endpoint was percentage of satisfaction of hair patient-reported outcome (SPRO) responders. ResultsSignificantly higher proportions of patients taking deuruxolitinib met the primary endpoint (8 mg 29.6%; 12 mg 41.5% versus placebo 0.8%). Both deuruxolitinib doses achieved significant improvements in all secondary endpoints versus placebo, including SPRO (8 mg 42.1%; 12 mg 53.0% versus placebo 4.7%). Most treatment-emergent adverse events were mild or moderate, consistent with other oral JAK inhibitors. LimitationsFurther studies are required to understand longer-term safety, efficacy, and impact of treatment cessation. ConclusionBoth doses of deuruxolitinib were effective for hair regrowth. Patient satisfaction aligned with hair growth.

A phase 1, open-label, dose escalation and dose expansion study to evaluate the safety, tolerability, pharmacokinetics, and antitumor activity of PF-07799544 (ARRY-134) as a single agent and in combination with PF-07799933 BRAF dimer inhibitor, in participants 16 years and older with advanced solid tumors.

TPS3180 Background: The MAPK pathway plays a role in several key signaling and phosphorylation events that contribute to tumorigenesis. Inhibition of MEK, along with RAF kinases, has proven to be a successful transformative strategy for melanoma and other MAPK pathway-altered tumors. However, the duration of clinical benefit is limited by a narrow therapeutic index, de novo and acquired resistance and poor brain penetration. PF-07799544 is a next-generation, fully brain penetrant MEK inhibitor. PF-07799933 is an oral selective ATP-competitive small-molecule RAF kinase inhibitor that suppresses BRAF signaling in BRAF V600-mutant and non-V600-BRAF mutant tumors. It displays significantly less paradoxical activation than approved BRAFi and is not “pan RAF” as it spares non-BRAF mutated-containing RAF dimers. We describe here the design of the Phase 1 study of PF-07799544 as Monotherapy or in Combination with a next generation BRAF dimer inhibitor PF-07799933 in participants with BRAF mutated (BRAFm) advanced solid tumors. Methods: The purpose of this first-in-human study is to investigate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics, and potential clinical benefits of PF-07799544 administered as a single agent in participants with advanced solid tumors (Phase 1a) and in combination with PF-07799933 in participants with BRAF Class 1, 2 and 3 mutated solid tumors with or without brain involvement (Phase 1b). Phase 1a will enroll participants with advanced solid tumors who have progressed on standard of care. The primary objective is to determine monotherapy MTD/RDE of PF-07799544. Once PK measurements indicate the potential for significant WT MEK mutation target coverage, participants with untreated and symptomatic brain metastases (bm) will be allowed to enroll. Phase 1b is comprised of multiple sub-studies, all of which evaluate PF-07799544 in combination with PF-07799933 in participants with BRAFm solid tumors who have progressed on standard of care therapies, including Class 1 BRAFi where indicated. Sub-study B: BRAFm melanoma (V600 and non-V600) will determine the MTDc/RDEc of the combination (Part 1 primary objective), followed by dose expansion cohorts (Part 2) (~80 participants): Cohort 1: BRAF V600 melanoma (asymptomatic and untreated bm permitted), Cohort 2: BRAF V600 melanoma (symptomatic bm), Cohort 3 BRAFm Class 2/3 melanoma (asymptomatic and untreated bm permitted); Sub-study C: BRAFm Class 2 or 3 advanced solid tumor Cohort 1 (asymptomatic and untreated bm permitted and Cohort 2 (symptomatic bm) (~20 each cohort). The main objectives of the dose expansion cohorts in all substudies, will be to evaluate anti-tumor activity, safety, PK and PD. Clinical trial information: NCT05538130 .

Depletion of histone H3K27 demethylase exerts anti-tumor activity as a monotherapy and in combination therapy with ceralasertib in non-small cell lung carcinoma.

e20035 Background: Lung cancer is one of the most frequently diagnosed cancers and is the leading cause of cancer-related death worldwide. Non-small cell lung carcinoma (NSCLC) represents 85% of lung cancers and is the most common type with poor prognosis. The lysine-specific demethylase UTX (gene name KDM6A) demethylates H3K27me2/3 at genes and enhancers and have been shown to support oncogenic transcription factors. We hypothesize that UTX is a highly pleiotropic factor in tumorigenesis and may plays a critical role in controlling DNA replication-associated gene activation as well as in replication stress-related DNA damage repair. Methods: To evaluate the role of UTX in tumorigenesis, shRNA-mediated UTX knockdown was employed in NCI-H1975 cells followed by cell cycle and cell proliferation assays. In the UTX-knocked down NCI-H1975 cells, target genes involved in DNA replication and DNA damage repair were discovered by RNA sequencing and further validated with RT-qPCR. Effects of UTX depletion on DNA replication and radiation-induced DNA repair were analyzed by immunofluorescence. Effects of UTX depletion on cell cycle arrest and the ATR–CHK1 checkpoint signaling pathway were analyzed by flow cytometry and immunoblotting. In vivo response to UTX inhibition monotherapy (UTX knockdown) and combination therapy of UTX knockdown with ceralasertib, a selective ATR kinase inhibitor, was evaluated in dox-inducible UTX knockdown NCI-H1975 xenografts. Results: Induction of UTX knockdown significantly reduced the NCI-H1975 tumor volume compared to the control group, showing anti-tumor activity. Furthermore, loss of UTX induced hyperactivation of ATR–CHK1 checkpoint signaling pathway, suggesting the UTX-depleted tumor cells attempt to alleviate replication stress to escape from apoptosis. To inhibit the UTX-depletion induced ATR–CHK1 pathway, ceralasertib (formerly AZD6738), an oral potent selective inhibitor of ATR, was combined with UTX-knockdown for in vitro and in vivo evaluation. Consistent with in vitro cell-based assay, combination therapy of ceralasertib with UTX depletion showed enhanced tumor growth inhibition and regression in the NCI-H1975 xenograft model. Conclusions: Our findings provide new insights into a pro-oncogenic role of UTX in supporting tumor maintenance via engaging DNA replication and repair pathway. Depletion of UTX alone may serve as a new therapeutic target in non-small cell lung carcinoma; and further combination with ceralasertib enhances the anti-tumor activity of UTX knockdown by inhibiting the ATR–CHK1 checkpoint signaling pathway.

Selpercatinib in non-MTC, RET-mutated tumors: Efficacy in MEN-associated and other tumors.

3150 Background: Selpercatinib, a first-in-class highly selective and potent RET kinase inhibitor with CNS activity, is approved in multiple countries for the treatment of RET-activated cancers. Current indications for RET mutant disease are limited to MTC. This analysis examined if selpercatinib was effective in non-MTC, RET mutation positive tumors and whether certain RET mutations demonstrated better activity (n=23; data cut-off: 13Jan2023). Methods: The phase 1/2 LIBRETTO-001 trial (NCT03157128) enrolled pts with locally advanced/metastatic RET-altered solid tumors, including pts with RET mutations in tumors other than MTC. Mutations must be known to be activating based on activity in MTC or other published evidence. Primary endpoint was objective response rate (ORR) by independent review committee (IRC). Secondary endpoints included ORR by investigator (INV), duration of response (DoR), progression-free survival (PFS), and safety. Results: Fourteen different tumor types were identified among the 23 pts with non-MTC RET-mutated tumors. This included 8 tumors from the Multiple Endocrine Neoplasia (MEN) syndrome spectrum; adrenal (pheochromocytoma; n=5), paraganglioma (n=2), neuroendocrine (n=1) (Table). Most of the mutations were located in extracellular cysteine-rich domain (CRD) and in the tyrosine kinase domain (TKD) of RET. In 23 efficacy-evaluable pts, confirmed ORR by IRC was 21.7% (5/23, 95% CI: 7.5, 43.7). ORR by IRC for pts with MEN-associated tumors (n=8) was 37.5% while five of these pts (62.5%) had stable disease lasting at least 16 weeks (SD16+). ORR by IRC for the sub-population with pheochromocytoma (n=5) was 40.0% and for pts with tumors manifesting RET extracellular cysteine mutations (n=5) was 60.0%. Of the 15 pts with non-MEN-associated tumors, 2 pts (8.7%; mutation in TKD) had a partial response (both with NSCLC adenocarcinoma, of which one had co-existent MTC). For the overall pts, the median DoR was 12.2 months (95% CI: 3.8, NE) and median PFS was 5.5 months (95% CI: 1.8, 19.4). No new safety signals were identified compared to previous reports. One grade 5 AE, general physical health deterioration, was observed and deemed by INV as not related to selpercatinib. Conclusions: This study suggests that RET-mutated, MEN-associated cancers (adrenal, paraganglioma, neuroendocrine) may benefit from selpercatinib treatment, which could be mediated through mutations in the extracellular CRD. The non-MTC RET-mutated tumor types appear not to derive benefit from selpercatinib. Clinical trial information: NCT03157128 . [Table: see text]

Phase I clinical study of FC084CSA, a high selective AXL kinase inhibitor that ameliorates tumor microenvironment and augments the effectivity of immunotherapy.

e15116 Background: NSCLC patients with STK11 gene mutations could not benefit from immunotherapy, according to the data of multiple clinical trials. This is associated with immunosuppressive tumor microenvironment (TME) due to elevated AXL expression, and deficiency in pro-inflammatory cytokines and effector T cells. AXL inhibitor bemcentinib (formerly BGB324) has been found to improve the effectiveness of immunotherapy of immune checkpoint inhibitors. FC084CSA is a high selective AXL inhibitor. Methods: This is an ongoing first-in-human, phase I study of FC084CSA in patients with advanced solid tumors. The primary objective is to evaluate the safety and tolerability of FC084CSA. The secondary objectives include preliminary efficacy and pharmacokinetics. Results: As of January 10th, 2024, 9 patients with a median age of 60 years (44-73) were enrolled in 4 different dose levels: 100mg QD, 200mg QD, 400mg QD and 600mg QD. All patients had ≥ 2 prior lines of prior therapy. No dosing-limiting toxicities were observed. 8 (88.9%) patients experienced treatment-related adverse events (TRAEs). Most TRAEs were grade 1 or 2 and only one grade 3 TRAE was observed. The most common TRAEs (≥20%) included increased blood lactate dehydrogenase (44.4%), elevated gamma-glutamyl transferase (33.3%), proteinuria (33.3%), anemia (33.3%), increased aspartate aminotransferase (22.2%), weight loss (22.2%), increased blood creatinine (22.2%) and vomiting (22.2%). A total of 8 patients had at least 1 post-baseline tumor assessment. Objective response rate (ORR) was 0% and disease control rate (DCR) was 62.5% (5/8). Conclusions: FC084CSA was well tolerated in patients with previously heavily treated solid tumors. Clinical trial information: NCT06231550 .

Lenvatinib rechallenge after failure of lenvatinib and sorafenib in metastatic thyroid cancer.

The oral multikinase inhibitors sorafenib and lenvatinib are currently available as first-line treatment for patients with unresectable or metastatic thyroid cancer. However, treatment options for patients who are refractory to these multikinase inhibitors are limited. This study aimed to evaluate the safety and efficacy of rechallenged lenvatinib after failure of both lenvatinib and sorafenib in patients with metastatic thyroid cancer in the real-world clinical practice. We retrospectively reviewed the data of consecutive 16 patients with metastatic thyroid cancer who received lenvatinib as a rechallenge after failure of initial lenvatinib and sorafenib treatment at Shizuoka Cancer Center between 2016 and 2023. Of these, the initial lenvatinib was discontinued in 12 patients owing to progressive disease, in 3 patients owing to adverse events, and in 1 patient owing to both. The overall response rate was 6.7%, and disease control was achieved by rechallenge with lenvatinib in all patients with the target lesions. The median progression free survival after rechallenging with lenvatinib was 15.0 months. No new signs of toxicity were observed after rechallenging with lenvatinib. Our findings suggest that rechallenge with lenvatinib after failure of both lenvatinib and sorafenib showed manageable safety and modest efficacy in patients with metastatic thyroid cancer in clinical practice. The strategy of lenvatinib rechallenge may provide an alternative option for patients with no targetable driver genes or when selective kinase inhibitors are not indicated.

Sensitive and selective electrochemical sensor for palbociclib, a highly selective CDK4/6 inhibitor, based on molecularly imprinted polymer

In this research, a molecularly imprinted polymer (MIP)-based electrochemical sensor was developed for the first time to determine palbociclib (PLB), an oral, selective Cyclin Dependent Kinase (CDK4 and CDK6) inhibitor used in the treatment of breast cancer. Acrylamide (ACR) was selected as the functional monomer to fabricate the proposed sensor (ACR-PLB-MIP/GCE), and polymerization was performed by photopolymerization. To improve the efficiency of the MIP-based electrode for PLB measurement, several factors, including monomer ratio, removal time, removal agent, and rebinding time, were carefully optimized. Under optimal conditions and using the differential pulse voltammetry (DPV) technique, the limit of detection (LOD) of 1.35 × 10−12 M and the limit of quantification (LOQ) of 4.48 × 10−12 M were calculated for PLB analysis using ACR-PLB-MIP/GCE in standard solution. Application of the ACR-PLB-MIP/GCE sensor to commercial serum samples resulted in LOD and LOQ values of 3.33 × 10−12 M and 1.11 × 10−11 M, respectively. The sensor was also applied to the tablet sample for the detection of PLB and a satisfactory RSD% (0.95) was obtained. The results of interference studies confirmed the high selectivity of the electrode for PLB analysis. These results clearly demonstrated that the molecular imprinting approach for the detection of PLB in the novel sensor system is a highly efficient approach.

Abstract PO1-16-04: Targeting PKMYT1 Kinase as a Therapeutic Strategy for Treatment of Triple Negative Breast Cancer with Low Molecular Weight Cyclin E (LMW-E) Expression

Abstract Purpose: Low molecular weight isoforms of cyclin E (LMW-E) have been implicated in various human cancers, including triple negative breast cancer (TNBC), and are associated with a poor prognosis. However, targeted therapies for TNBC based on biomarkers are currently lacking. This study aims to investigate LMW-E as a potential therapeutic target in TNBC and evaluate the efficacy of RP-6306, a selective inhibitor of the Protein Kinase, Membrane Associated Tyrosine/Threonine 1 (PKMYT1), in LMW-E-positive breast tumors. Experimental Design: Immunohistochemical (IHC) analysis was performed on pre-treatment tumor specimens from TNBC patients (n=36) to assess the correlation between LMW-E expression, CDK1 phosphorylation at Threonine 14 (pT14), and pathologic complete response to neoadjuvant chemotherapy. LMW-E inducible human mammary epithelial cells (hMEC) and breast cancer cell lines were used to investigate the regulatory effect of LMW-E on PKMYT1, the kinase responsible for CDK1 phosphorylation at T14, and the response to RP-6306, a first in-class and selective inhibitor of PKMYT1. Patient-derived xenograft (PDX) models and transgenic mouse mammary tumor virus (MMTV) models of TNBC expressing human LMW-E (hLMW-E) were also utilized to assess LMW-E as a biomarker for predicting response to RP-6306. Results. Analysis of TNBC tumor biopsies revealed a significant positive correlation between LMW-E expression and CDK1 pT14, and both biomarkers were associated with a lack of pathological complete response to neoadjuvant chemotherapy. In vitro results using LMW-E inducible hMECs and breast cancer cell lines demonstrated that LMW-E up-regulates PKMYT1 and CDK1 pT14, acting as a PKMYT1 binding protein and enhancing PKMYT1 protein stability. High LMW-E protein levels predicted a favorable response to RP-6306, resulting in the accumulation of sub-G1 and polyploid cells, decreased tolerance to replication stress, increased DNA damage, chromosomal breakage, and apoptosis. In vivo treatment of TNBC PDX models and hLMW-E transgenic tumors with RP-6306 resulted in a significant reduction in tumor volume only in mice harboring high LMW-E tumors, while low cyclin E models showed no response. Immunohistochemical analysis confirmed increased γ-H2AX and decreased CDK1-pT14 and Ki67 levels, indicating the efficacy of RP-6306 in both PDX and transgenic models. Conclusion: This study highlights the regulatory axis from LMW-E to PKMYT1 and its predictive value for pathological complete response in TNBC patients receiving neoadjuvant chemotherapy. The selective PKMYT1 kinase inhibitor RP-6306 consistently induced DNA damage and inhibited tumor growth in in vitro and in vivo pre-clinical breast tumor models. Co-expression of LMW-E and CDK1-pT14 in TNBC can be used to stratify patients whose tumors are likely to respond to RP-6306, emphasizing its therapeutic significance. Citation Format: Mi Li, Amriti Lulla, Cansu Karakas, Spiridon Tsavaschidis, Yan Wang, Tuyen Nguyun, Tuyen Bui, Gary Marshall, Kelly Hunt, Khandan Keyomarsi. Targeting PKMYT1 Kinase as a Therapeutic Strategy for Treatment of Triple Negative Breast Cancer with Low Molecular Weight Cyclin E (LMW-E) Expression [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 PO1-16-04.

Abstract PO4-05-09: Phase I study of the FGFR inhibitor rogaratinib, fulvestrant and palbociclib in advanced hormone receptor-positive (HR+) breast cancer (BC) with FGFR1/2 amplification and/or overexpression (FGFR1/2+)

Abstract Background: Novel therapies are needed upon progression to first-line CDK4/6 inhibitor (CDK4/6i) plus aromatase inhibitor (AI) in advanced HR+ BC. One frequent alteration driving resistance to CDKi plus AI is FGFR1/2 amplification or overexpression. In preclinical FGFR1/2+ HR+ BC models, combined CDK4/6, ER and FGFR blockade was more effective than single- or double combinations (Breast Cancer Res; 23:21-37; 2021). Rogaratinib (ROGA) is a selective FGFR1-4 kinase inhibitor with significant activity in FGFR-aberrant tumors. We aimed to study the tolerability and preliminary efficacy of ROGA added to fulvestrant (FUL) and palbociclib (PAL) in patients (pts) with FGFR1/2+ HR+ BC progressing on first-line CDK4/6i plus AI. Methods: ROGABREAST (NCT04483505) was a single-arm, prospective, multicentric, open-label, phase I dose-escalation trial following a classic 3+3 schedule. Pts were pre-screened for FGFR1/2 amplification and/or overexpression by FISH and RNAScope. Women >18 year-old with advanced HR+ BC progressing on first-line CDI4/6i plus AI, and adequate organ function were included. Pts received ROGA monotherapy q12 hours in day 1. In day 2, pts continued ROGA and started FUL (500 ug IM) plus PAL (100 mg/day on days 1-21). FUL was repeated in day +15. Cycle 1 was 29 days-long and followed by 28-day cycles (continuous ROGA q12 hours days 1-28, FUL 500 ug day 1, and PAL 100mg/d days 1-21). Level 1 was ROGA 400 mg/bid and escalated 200 mg/bid increments. FUL dose was not modified. PAL was allowed to escalate intrapatient to 125 mg/d after cycle 2 in pts experiencing ≤ grade 1 tolerable side effects as the greatest toxicity in cycle 1. PK and PD (FGF23 and phosphate levels) profiles were obtained in days +1 and +15. DLT-assessment period was cycle 1-2. Results: from 12/2020 to 5/2022, 67 pts were screened; 29 were FGFR1/2+ (22 and 5 RNAscope-positive for FGFR1 and FGFR2; 17 and 3 FISH-positive for FGFR1 and FGFR2). Nine pts entered the study. Six were enrolled in level 1, where 1 DLT (grade 3 diarrhea) occurred, and 3 in level 2 (600 mg ROGA bid; no DLTs). Grade 3 hyperphosphatemia, adequately controlled with diet and chelants (33% of the patients) and grade 2 non-tolerable dactylitis/onycholysis (11%) were the most frequent severe toxicities after the DLT period. Other toxicities were mild and well-tolerated (grade 1-2 diarrhea and hyperphosphatemia occurred in 66 and 44% of the pts, respectively). Median PFS was 113 days and 44% of the pts had a PFS > 180 days, with no apparent relationship with FGFR1 or 2 status, or mutations found via WES. The trial was terminated after completion of level 2 due to rogaratinib development discontinuation. Conclusions: Triple FGFR1/2, CDK4/6 and ER blockade appears safe at standard drug dosages and shows promising clinical activity in second-line HR+ FGFR1/2+ BC patients progressing on CDK4/6i plus AI. Citation Format: Noelia Martínez-Jáñez, Sonia Pernas, José Ángel García-Sáenz, Serafin Morales Murillo, Begoña Bermejo, Juan A Guerra, Silvana Mouron, Miguel Quintela-Fandino. Phase I study of the FGFR inhibitor rogaratinib, fulvestrant and palbociclib in advanced hormone receptor-positive (HR+) breast cancer (BC) with FGFR1/2 amplification and/or overexpression (FGFR1/2+) [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 PO4-05-09.

Abstract PO2-24-10: Anti-Tumorigenic Immuno-Microenvironment by AB-329, a Potent and Selective AXL inhibitor, combined with paclitaxel in Triple-Negative Breast Cancer Preclinical Model

Abstract BACKGROUND The Gas6/AXL signaling pathway plays a substantial role in cancer cell survival, proliferation, immunosuppression, and metastasis. Elevated AXL expression is associated with advanced cancer stages and decreased overall survival rates, underscoring its potential as a therapeutic target for metastatic cancers. We investigated this possibility by utilizing AB-329, a selective small molecule AXL kinase inhibitor, to treat triple-negative breast cancer (TNBC). TNBC, typified by the lack of ER, PR, and HER2 expression, frequently displays mesenchymal characteristics and carries a significant risk of metastasis and an immunosuppressive tumor microenvironment. METHODS We assessed AXL protein expression in 28 human and 11 mouse breast cancer cell lines using Western blotting. The Microarray database was utilized to examine AXL gene expression in 40 human breast cancer cells. The Sulforhodamine B proliferation and soft agar assays measured the antiproliferative effect of AB-329 in TNBC cell lines. The in vitro anti-metastatic impact of AB-329 was evaluated through migration and invasion assays. We appraised the anti-tumor effects of AB-329 in combination with paclitaxel using 4T1 and E0771-LMB mouse TNBC xenograft models. We used FACS and CIBERSORTx to perform immune cell type profiling in E0771-LMB xenograft tumor tissues. To understand AB-329’s immunomodulatory effects in tumors, single-cell RNA sequencing was conducted in a humanized mouse model with SUM149 human TNBC xenografts. RESULTS Microarray data revealed higher AXL expression in TNBC cells compared to non-TNBC cells. Western blotting supported this, showing higher AXL protein expression, particularly in basal and mesenchymal subtypes of TNBC cells, compared to luminal breast cancer cells. AB-329 presented moderate antiproliferative effects as a monotherapy in the TNBC cell lines tested, with half-maximal inhibitory concentrations exceeding 5 µM. Nevertheless, combining AB-329 with paclitaxel resulted in significant growth inhibition in all tested TNBC cell lines (p < 0.05). Importantly, AB-329 alone could inhibit TNBC migration and invasion at a concentration of 1 µM (p < 0.01) and showed enhanced inhibition rates when paired with paclitaxel (p < 0.05). The combination of AB-329 and paclitaxel considerably reduced tumor growth in the 4T1 and E0771-LMB xenograft models compared to paclitaxel or AB-329. Total RNA sequencing and CIBERSORTx analysis indicated that the AB-329 and paclitaxel combination increased Natural Killer (NK) cells’ infiltration into E0771-LMB mouse TNBC xenograft tumors compared to single agent-treated tumors. A nearly 2.5-fold increase in NKT cell infiltration was also detected with AB-329 treatment compared to Control in SUM149 human TNBC xenografts. CONCLUSIONS Our preclinical data suggest that AB-329, an AXL inhibitor, could synergize effectively with paclitaxel in TNBC treatment, notably inhibiting tumor cell proliferation and migration while enhancing NK cell infiltration. Intriguingly, we observed an increased infiltration of NKT cells into tumors following AB-329 treatment, which may promote an anti-tumorigenic immuno-microenvironment. These results underscore the necessity for further investigation into the role of AB-329 in modulating the tumor immuno-microenvironment through AXL pathway inhibition and accentuate the potential for combining AB-329 with immunotherapy. Citation Format: Dileep Reddy Rampa, Jon Fuson, Huey Liu, Max Pan, Naoto Ueno, Jangsoon Lee. Anti-Tumorigenic Immuno-Microenvironment by AB-329, a Potent and Selective AXL inhibitor, combined with paclitaxel in Triple-Negative Breast Cancer Preclinical Model [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 PO2-24-10.

Rapid and sustained improvements in itch and quality of life with upadacitinib plus topical corticosteroids in adults and adolescents with atopic dermatitis: 52-week outcomes from the phase 3 AD Up study

Purpose: Atopic dermatitis (AD) adversely impacts quality of life (QoL). We evaluated the effect of upadacitinib, an oral selective Janus kinase inhibitor approved for moderate-to-severe AD, plus topical corticosteroids (+TCS) on patient-reported outcomes (PROs) over 52 weeks. Materials and methods: In the phase 3 AD Up study (NCT03568318), adults and adolescents with moderate-to-severe AD were randomized 1:1:1 to once-daily upadacitinib 15 mg, 30 mg, or placebo + TCS. Itch, skin pain/symptoms, sleep, QoL, daily activities, emotional state, mental health, and patient impressions of disease severity/improvement/treatment satisfaction were assessed. Results: This analysis included 901 patients. Within 1–2 weeks, PRO improvements were greater with both upadacitinib doses than with placebo (p <.05). Improvements increased through weeks 4–8; rates were generally maintained through week 52. At week 52, the proportion of patients with clinically meaningful improvements in itch (Worst Pruritus Numerical Rating Scale improvement ≥4), skin pain (AD Symptom Scale Skin Pain improvement ≥4), sleep (AD Impact Scale [ADerm-IS] Sleep improvement ≥12), daily activities (ADerm-IS Daily Activities improvement ≥14), and emotional state (ADerm-IS Emotional State improvement ≥11) ranged from 62.1%–77.7% with upadacitinib 15 mg + TCS and 71.3%–83.6% with upadacitinib 30 mg + TCS. Conclusions: Upadacitinib + TCS results in rapid, sustained improvements in burdensome AD symptoms and QoL.

LIBRETTO-431: Confirming the Superiority of Selpercatinib to Chemotherapy and the Lack of Efficacy of Immune Checkpoint Inhibitors in Advanced RET Fusion-Positive (RET+) NSCLC, Another Unique Never-Smoker Predominant Molecular Subtype of NSCLC.

Selpercatinib, a potent and highly selective RET kinase inhibitor with significant CNS activity, has recently gained US approval for the treatment of NSCLC harboring RET fusions (RET+) based on a large-scale single-arm study. The LIBRETTO-431 trial was the global pivotal registration phase 3 trial comparing selpercatinib to platinum-based chemotherapy with or without pembrolizumab as the first-line treatment of patients with advanced RET+ NSCLC. Never-smokers constituted 67.4% of the RET+ NSCLC patients enrolled. KIF5B-RET made up the vast majority (77%) of the RET+ fusion variant with known fusion partner. The results of this study demonstrated significant improvement in progression-free survival (PFS) benefit as well as impressive intracranial disease response in participants treated with selpercatinib as compared to those treated with chemotherapy, with a HR [hazard ratio] of 0.46 (95% CI 0.33-0.70; P < 0.001) for the intention-to-treat (ITT)-pembrolizumab group and HR of 0.46 (95% CI 0.31-0.70, P < 0.001) for the overall ITT-group of patients. The addition of pembrolizumab to platinum/pemetrexed chemotherapy resulted in numerically identical PFS (11.2 months). These results point to selpercatinib's superiority to traditional chemotherapy regimens in the treatment of NSCLC harboring RET fusions and add to literature on the salience of targeted precision oncology and lack of efficacy of immune checkpoint inhibitor in NSCLC patients with never-smoker predominant actionable driver mutations. RET+ NSCLC should be added to the list of molecular subtypes (EGFR+, ALK+, ROS1+) of NSCLC to be excluded in chemoimmunotherapy trial.