Inappropriate activation of the mitogen-activated protein kinase (MAPK) pathway, often stemming from activating mutations in RAS or RAF, represents one of the most common oncogenic events in human cancer. However, currently approved RAS/RAF inhibitors target specific mutants that are only present in a small proportion of RAS- or RAF-activated tumors. Current MEK inhibitors (MEKi) are associated with class-effect toxicities and tumor escape via CRAF bypass of MEK blockade. To address these issues, we designed atebimetinib to resist CRAF-mediated bypass and enable a pharmacokinetic/pharmacodynamic (PK/PD) profile termed deep cyclic inhibition (DCI), an approach that transiently but deeply suppresses oncogenic signaling while allowing daily physiologic reset. Unlike chronic or intermittent approaches, DCI optimized depth and duration of MEK suppression on a daily cycle, blunting rebound signaling while preserving recovery windows for normal tissues. Functioning as an allosteric, selective MEKi, atebimetinib potently inhibited ERK phosphorylation in vitro and in vivo, resisted CRAF bypass, and was well tolerated and more efficacious in xenograft models of cancer compared with current MEK inhibitors. Overall, these findings establish atebimetinib as a dual-MEK inhibitor with the potential to provide mutation-agnostic inhibition of the MAPK pathway while leveraging DCI, designed to avoid toxicities associated with existing MEK inhibitors. Atebimetinib offers MEK inhibition that is durable and tolerable, supporting the potential of this therapeutic paradigm.

Objectives: Activating RAS mutations are present in a third of all cancers. Approved MEK inhibitors chronically inhibit the downstream signaling of RAS, causing significant toxicity. IMM-1-104 was designed to have high oral bioavailability and a short half-life with a near-zero drug trough, to achieve Deep Cyclic Inhibition (DCI). Preclinical data indicated that DCI can significantly improve the safety margin by allowing daily pathway recovery in healthy tissues while limiting adaptive resistance in tumor cells (1). The current analysis was aimed at identifying Phase 2 dosing regimens that achieve the desired DCI pattern in the targeted patient populations. Methods: First-in-human Study IMM1104-101 recently completed Phase 1 dose expansion (2,3). PK/PD sampling was performed after overnight fasting, pre-dose and at 0.25, 0.5, 1, 1.5, 2, 4, 6, 8 and 24 h post-dose, on Days 1 and 15 of the study (1-24 h for PD). An ex-vivo surrogate PD endpoint was the inhibition of MEK and downstream ERK phosphorylation in the A549 (KRAS-G12S) cell line, expressed as the ratio of phosphorylated/total kinase, relative to pre-dose baseline. Non-compartmental analysis and population PK/PD analysis were performed using Phoenix 8.3 and NONMEM 7.5, respectively. Results: Interim PK data are available from 21 out of 45 participants treated with IMM-1-104 as single agent at daily doses of 40 (n=1), 80 (n=1), 160 (n=3), 240 and 320-mg (n=8 each). While most PK profiles showed a rapid absorption with tmax within 1 h of dosing, a two-compartment model with first-order absorption and lag time plus first-order elimination best described the interim PK dataset. Weight-based allometric scaling was applied to clearance, distribution volume and inter-compartmental clearance. The mean elimination half-life at steady-state ranged from 1.4-2.5 h across doses, without indications of non-linearity. Less than 5% of unchanged IMM-1-104 is renally cleared. PD assay results correlated to IMM-1-104 plasma concentrations, with maximal inhibition (target engagement) achieved mostly at 1 h, returning to baseline phospho-ERK (pERK) levels between 8 and 24 h. A direct Imax model, with a Hill coefficient fixed to 1, could be successfully applied to describe PK/PD and to calculate time above and below selected inhibitory concentrations. The derived pERK IC50 of 102 ng/mL (48 nM unbound) corresponded well with in vitro pERK inhibition data. Conclusion: At the two candidate doses explored per FDA Optimus guidance, 240 and 320 mg, plasma concentrations are predicted to be above the pERK IC90 for on average approximately 1.5 and 2.5 h, respectively, and the vast majority of patients are predicted to have less than 20% of maximum inhibition at the daily drug trough (87% at 240 mg once daily and 84% at 320 mg). PK/PD modeling combined with Phase 1 safety and activity data suggests that 240 and 320 mg are viable doses that promote DCI of the MAPK pathway.Citations: [1] P Nair et al, Predicting activity of IMM-1-104 as single agent and in combination for patients with RAS or RAF mutant tumors, AACR-NCI-EORTC 2023.[2] A Phase 1/2a Study of IMM-1-104 in Participants with Previously Treated, RAS-Mutant, Advanced or Metastatic Solid Tumors - NCT05585320.[3] V Chung et al, Preliminary phase 1 safety and activity of IMM-1-104, an orally dosed universal RAS inhibitor that drives deep cyclic inhibition of the MAPK pathway at MEK, in patients with advanced unresectable or metastatic solid tumors - ESMO 2024, submitted.

Abstract Introduction: Addiction to the MAPK pathway drives a large proportion of cancers, and pancreatic tumors almost universally display RAS mutations. IMM-1-104, a once-daily oral treatment being evaluated in a Phase 1/2a trial for RAS-mutant solid tumors [NCT05585320], offers a novel deep cyclic inhibition (DCI) approach in targeting the MAPK pathway at MEK. Traditionally, MAPK-targeted drugs inhibit the pathway chronically causing serious class-effect toxicities and limited durability due to resistance. In contrast, IMM-1-104’s unique pharmacokinetic (PK) profile was designed to drive pulsatile MEK inhibition, with the goal of improving tolerability and providing more durable activity across a broad range of MAPK-driven tumors. Phase 1 dose escalation of IMM-1-104 revealed no dose-limiting toxicities, high oral bioavailability, plasma half-life of approximately 2-hours, and pharmacodynamic (PD) data supporting DCI of the MAPK pathway. Experimental Procedures: IMM-1-104 responses in humanized 3D tumor growth assays (3D-TGA) were combined with NGS data using machine learning (ML) to refine a pharmacogenomic response model. Evaluation of databases such as AACR Project GENIE enabled prediction of patient alignment of preclinical models based on genomic profile, identification of patient populations displaying MAPK pathway addiction and projected sensitivity to IMM-1-104 mono- or combination therapy. To test combinations with approved chemotherapy agents, IMM-1-104, gemcitabine (GEM) and nab-paclitaxel (PAC) and 5-fluorouracil (5FU) were evaluated in tumor xenograft models with drugs alone or across multiple combinations. Summary of New Data: IMM-1-104 showed promising combination effects when treated with GEM or PAC in 3D-TGA pancreatic cancer models. In a MIA PaCa-2 tumor xenograft model, IMM-1-104 alone showed greater tumor growth inhibition (TGI) than any single or combination chemotherapy tested. Further, combinations of IMM-1-104 plus chemotherapy resulted in near complete responses in a majority of animals. At day 39, antitumor activity (TGI%) was 103% for IMM-1-104 at 125 mg/kg BID PO, 25.2% for GEM at 60 mg/kg IP Q4D, 62.2% for PAC at 10 mg/kg IV Q4D and 36.6% for 5FU at 50 mg/kg IP Q4D. Based on these results and additional 3D-TGA pharmacogenomics data, ML modeling was advanced to query the GENIE database and identify biomarkers of response and resistance with the goal of further informing mono and combination treatment options with IMM-1-104 in pancreatic cancer. Conclusions: The Phase 2a portion of the ongoing IMM-1-104 clinical study includes five arms, three of which focus on patients with pancreatic cancer, where IMM-1-104 will be evaluated as both monotherapy and in select combinations with approved chemotherapeutic agents. The new in vitro, in vivo and ML modeling data presented here further support an advancing translational roadmap for IMM-1-104 in pancreatic cancer. Citation Format: Peter King, Jason Funt, Sarah Kolitz, Praveen Nair, Jan de Jong, Amy Yamamura, Mai Johnson, Jenny Zhang, Kevin Fowler, Anna Travesa, Amy Axel, Chris Walker, Benjamin J. Zeskind, Brett M. Hall. Activity of IMM-1-104 alone or in combination with chemotherapy in RAS-altered pancreatic cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4195.

Drug sensitivity of NSCLC specimens to HDAC inhibitors and combination with standards of care.

Abstract Introduction: Many tumors are addicted to MAPK pathway activation, including the >20% of human tumors with mutations in RAS or RAF1. IMM-1-104 is an oral once-daily treatment currently in Phase 1 in patients with RAS-mutant solid tumors [NCT05585320]. To date, drugs disrupting the MAPK pathway have done so chronically, leading to dose-limiting toxicities (DLTs) and poor response durability. In contrast, IMM-1-104 was designed to provide deep cyclic inhibition (DCI) of the MAPK pathway via a unique pharmacokinetic (PK) profile with high peak plasma drug levels and a near zero drug trough between doses. This promotes pulsatile inhibition of MEK, depriving tumors of sustained signaling of a critical oncogenic pathway while limiting toxicity and durability issues associated with chronic MEK inhibition. In Phase 1a dose escalation, no DLTs were observed, the plasma drug half-life was ~2-hours, and pharmacodynamic (PD) data were consistent with DCI. Phase 1b dose expansion is underway. Translational efforts are focused on identifying MAPK pathway addiction and sensitivity to IMM-1-104. Tumor models displaying patient-aligned genomic profiles against large patient databases such as AACR Project GENIE1 were tested in humanized 3D tumor growth assays (3D-TGA). Computational modeling based on response and in-house genomic data was used to inform identification of patient populations for IMM-1-104 monotherapy and potential combination opportunities. Experimental Procedures: Using cancer-specific, patient-aligned cell lines, IMM-1-104 activity was characterized in the 3D-TGA. Whole exome sequencing was performed to confirm alteration status, and a further subset subjected to RNA sequencing. Pharmacogenomic data were used to generate a model predictive of response to IMM-1-104 and identify biomarker-aligned patient subpopulations. Selected model predictions were then tested in subcutaneous tumor xenograft models in female BALB/c nude mice. Summary of New Data: Assessment of IMM-1-104 across >190 patient-aligned models demonstrated diverse responses across a wide range of MAPK-driven tumor types, including those with RAS or RAF mutations. In addition to RAS, these data suggested additional potential for IMM-1-104 in BRAF-mutant disease. Therefore, IMM-1-104 was tested alone and with encorafenib in the HT-29 colorectal BRAFV600E mutant xenograft model. Monotherapy with either encorafenib or IMM-1-104 displayed superior tumor growth inhibition to binimetinib. IMM-1-104 in combination with encorafenib drove deeper regressions and superior durability of response in a head-to-head in vivo comparison versus binimetinib plus encorafenib. Conclusions: We used an integrated platform of translational experiments and informatics to identify patient-aligned model systems, prioritize factors relevant for response to IMM-1-104’s unique DCI profile, and elucidate combination opportunities to potentially inform clinical development strategies. Citation Format: Praveen Nair, Sarah Kolitz, Jason Funt, Jan de Jong, Peter King, Amy Yamamura, Mai Johnson, Jenny Zhang, Kevin D Fowler, Anna Travesa, Amy Axel, Chris Walker, Scott Barrett, Benjamin J Zeskind, Brett Hall. Predicting activity of IMM-1-104 as single agent and in combination for patients with RAS or RAF mutant tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A134.

HGF expression in CAFS and MSCs.

JNJ-42756493 anti-proliferative activity against cancer cells lines from multiple origins.. Detailed data supporting Figure 2.

Growth of NSCLC specimens in the 3D-TGA.

Supplementary Figure 2 from Response prediction to a multitargeted kinase inhibitor in cancer cell lines and xenograft tumors using high-content tyrosine peptide arrays with a kinetic readout

Introduction: A significant proportion of cancer patients have tumors addicted to uncontrolled MAPK signaling. Activating mutations in RAS or RAF are often directly responsible and have been observed in over 20% of human tumors1. Because MEK is downstream of RAS and RAF, it is an appealing drug target. However, MEK inhibitors have historically suffered from poor clinical durability, high toxicity and a susceptibility to pathway reactivation that has limited monotherapy activity in the RAS mutant setting. Unlike other MEK inhibitors, IMM-1-104 [NCT05585320] and IMM-6-415 are designed with distinctive features including both (1.) a unique target engagement mechanism that helps resist MAPK pathway reactivation and (2.) a pharmacokinetic (PK) profile that enables fast cadence deep cyclic inhibition (DCI). DCI drives pulsatile targeted inhibition that deprives tumor cells of a critical oncogenic pathway while limiting drug-related toxicities by affording normal cells an adequate PK recovery window between drug doses. To our knowledge, IMM-6-415’s preclinical activity is driven by the shortest drug plasma half-life (0.3-hours in mice) of any MEK inhibitor developed to date. Experimental Procedures: IMM-6-415 has already demonstrated promising activity in RAS-mutant xenograft tumor models (SITC 2022). Here, the antitumor activity of IMM-6-415 was evaluated in over 60 humanized 3D tumor growth assays (3D-TGA), which included 30 BRAF class I-mutant tumor models. Additionally, multiple drug-drug combinations have been explored, including vertical drug combinations with BRAF inhibitors. IMM-6-415, binimetinib and encorafenib were tested head-to-head as single agents and in combination with encorafenib in BRAFV600E melanoma and colorectal subcutaneous tumor xenograft models in female BALB/c nude mice. Summary of New Data: As monotherapy, IMM-6-415 demonstrated antitumor activity in over 50% (34 of 66) of the 3D-TGA models tested, including 30 BRAF-mutant preclinical models in which 19 (63%) showed activity. Therefore, we further explored both monotherapy and combination activity of IMM-6-415 in the A-375 (melanoma) and HT-29 (colorectal) BRAF V600E tumor xenograft models. Monotherapy treatment with encorafenib or IMM-6-415 displayed superior tumor growth inhibition (TGI) when compared to binimetinib. Furthermore, the combination of IMM-6-415 plus encorafenib prompted greater TGI with superior durability of response when tested head-to-head against the combination of binimetinib plus encorafenib in vivo at human equivalent doses for registered drugs. Conclusions: IMM-6-415 demonstrated promising activity and tolerability in preclinical models alone and in combination with encorafenib. In combination with encorafenib, IMM-6-415 achieved a greater TGI in vivo than the combination of encorafenib plus binimetinib in BRAFV600E colorectal cancer and melanoma tumor models, suggesting an opportunity for IMM-6-415 as monotherapy or in combination in BRAF mutant tumors. Citation Format: Anna Travesa, Mai Johnson, Peter King, Praveen Nair, Jason Funt, Sarah Kolitz, Kevin D Fowler, John Brothers II, Amy Axel, Scott Barrett, Benjamin J Zeskind, Brett Hall. Deep Cyclic Inhibition of the MAPK pathway with IMM-6-415, alone and in combination with encorafenib, demonstrates anti-tumor activity and tolerability in RAF mutant tumors in vivo [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A093.

A schematic of the patient derived 3D-TGA method.

Efficacy of JNJ-42756493 against human tumor xenograft models from different origins and FGFR alteration status. Mice bearing xenograft tumors (100-200mm3) were treated with 25mg/kg of JNJ-42756493 QD for indicated time and percent tumor growth inhibition (%TGI) compared to vehicle treated animal calculated at end of treatment.

A) Structure of JNJ-42541707, a structurally related compound to JNJ-42756493. B) 72h growth inhibition (IC50) of JNJ-42541707 against 236 cancer cell lines from multiple origins color coded based on FGFR1,2,4 mRNA overexpression and FGFR WT.

Achievable peak serum concentration of chemotherapies in humans and associated references.

Supplementary Table 1 from Response prediction to a multitargeted kinase inhibitor in cancer cell lines and xenograft tumors using high-content tyrosine peptide arrays with a kinetic readout

Drug sensitivity of NSCLC specimens to standard of care reagents.

The purity of human epithelial tumour cells entered into the 3D-TGA.