A Phase II study of ERK inhibition by ulixertinib (BVD-523) in Metastatic Uveal Melanoma

PURPOSE

Uveal melanoma is a rare and aggressive subset of melanoma that is minimally responsive to traditional therapies. Greater than 80% of uveal melanomas have a mutation in GNAQ or GNA11 which lead to downstream signaling through the MAPK pathway. Ulixertinib (BVD-523) is a potent and reversible small molecule ATP-competitive inhibitor of both ERK1 and ERK2 protein kinases.

PATIENTS AND METHODS

We performed a phase II study to determine the efficacy and safety of BVD-523 in patients with metastatic uveal melanoma. This was conducted as a Simon two-stage design with a sample size of 25 patients (pts) and an initial evaluation of efficacy after 13 pts.

RESULTS

From April 2018 to April 2019 thirteen pts were enrolled. Pts were predominantly female (69%) with a median age of 64 years (34 -76). Sites of metastases included liver (84.6%) and lung (30.8%). Grade 3 and 4 toxicities associated with therapy were consistent with ERK inhibitors and included LFT elevation, hyponatremia, pruritis, amylase elevation, anemia and rash. The best response, per RECIST 1.1, was stable disease in 4 pts, and disease progression in 7 patients. Two patients were unevaluable for response due to withdrawal from study. Median time to progression was 2.0 months. There were eight deaths due to disease progression with a median overall survival of 6.9 months.

CONCLUSIONS

ERK inhibition with ulixertinib (BVD-523) did not demonstrate activity in patients with metastatic uveal melanoma. The toxicities observed were consistent with what would be expected with MAPK pathway inhibition.

Combined KRAS-MAPK pathway inhibitors and HER2-directed drug conjugate is efficacious in pancreatic cancer

Targeting the mitogen-activated protein kinase (MAPK) cascade in pancreatic ductal adenocarcinoma (PDAC) remains clinically unsuccessful. We aim to develop a MAPK inhibitor-based therapeutic combination with strong preclinical efficacy. Utilizing a reverse-phase protein array, we observe rapid phospho-activation of human epidermal growth factor receptor 2 (HER2) in PDAC cells upon pharmacological MAPK inhibition. Mechanistically, MAPK inhibitors lead to swift proteasomal degradation of dual-specificity phosphatase 6 (DUSP6). The carboxy terminus of HER2, containing a TEY motif also present in extracellular signal-regulated kinase 1/2 (ERK1/2), facilitates binding with DUSP6, enhancing its phosphatase activity to dephosphorylate HER2. In the presence of MAPK inhibitors, DUSP6 dissociates from the protective effect of the RING E3 ligase tripartite motif containing 21, resulting in its degradation. In PDAC patient-derived xenograft (PDX) models, combining ERK and HER inhibitors slows tumour growth and requires cytotoxic chemotherapy to achieve tumour regression. Alternatively, MAPK inhibitors with trastuzumab deruxtecan, an anti-HER2 antibody conjugated with cytotoxic chemotherapy, lead to sustained tumour regression in most tested PDXs without causing noticeable toxicity. Additionally, KRAS inhibitors also activate HER2, supporting testing the combination of KRAS inhibitors and trastuzumab deruxtecan in PDAC. This study identifies a rational and promising therapeutic combination for clinical testing in PDAC patients.

Abstract 2693: Combining ulixertinib (ERK1/2 Inhibitor) with EGFR and BRAF inhibition yields significant efficacy in preclinical BRAFV600E mutant colorectal cancer models

The BRAFV600E mutation occurs in approximately 7% of colorectal cancer (CRC). BRAF plus EGFR inhibition (encorafenib with cetuximab) is an FDA approved treatment option for adult patients with metastatic CRC. Ultimately, patients develop resistance leading to disease progression. The addition of a MEK inhibitor, binimetinib, did not confer overall survival benefit. We hypothesized that addition of ERK inhibition would increase magnitude and duration of response to BRAF plus EGFR inhibition by overcoming MAPK-related acquired resistance mechanisms. ERK is the terminal master regulator kinase of the RAS-MAPK pathway, therefore, targeting this node is likely to be effective in the context of numerous mechanisms of acquired resistance that reactivate the MAPK pathway.

Ulixertinib (BVD-523) is a first-in-class and best-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other therapeutics. Ulixertinib has demonstrated efficacy in patients with tumors harboring alterations within the RAS-MAPK pathway. The efficacy of ulixertinib, in combination with EGFR inhibition (cetuximab), plus BRAF inhibition (encorafenib), was assessed in CRC cell line derived xenograft models harboring BRAFV600E mutations. The triple combination resulted in superior tumor growth inhibition compared to dosing of any single agent or doublet. RNA sequencing was performed on treated tumor samples. Expression of the mutant BRAF allele was readily confirmed from RNA sequencing data. Gene expression analysis showed differential expression of MAPK pathway genes in triple combination treated groups versus single or doublet therapy.

A complete response to ulixertinib in combination with cetuximab and encorafenib for the treatment of a patient with metastatic CRC has been reported (Stuhlmiller, Timothy Joseph, et al. "Updated clinical outcomes from ULI-EAP-100, an intermediate expanded access program for ulixertinib (BVD-523)." (2022): e15101-e15101). The patient was treated under the Expanded Access Protocol (NCT04566393) for compassionate use access to ulixertinib. Preclinical data and clinical complete response warrants further investigation of ulixertinib plus BRAF and EGFR inhibition.

Citation Format: Deborah Knoerzer, Anupama Reddy, Jessica A. Box, Anna Groover, Brent Kreider, Martin Teresk, Caroline M. Emery. Combining ulixertinib (ERK1/2 Inhibitor) with EGFR and BRAF inhibition yields significant efficacy in preclinical BRAFV600E mutant colorectal cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2693.

Abstract 2692: The combination of ulixertinib (ERK1/2 Inhibitor) and KRASG12C inhibition demonstrates significant efficacy in preclinical models

Ulixertinib (BVD-523) is a first-in-class and best-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other therapeutics. Ulixertinib has demonstrated efficacy in patients with tumors harboring alterations within the RAS-MAPK pathway. KRAS is the most frequently mutated oncogene in cancer and is a key mediator of the RAS-MAPK signaling pathway resulting in proliferation and cellular growth. The specific KRASG12C mutation occurs in approximately 10% of non-small cell lung cancer (NSCLC), 3% of colorectal cancer, and 1-2% across all other tumor types. KRASG12C mutant-inhibitors, including AMG-510 (sotorasib), MRTX849 (adagrasib), and JDQ443 have demonstrated efficacy in KRASG12C-mutant cancers, including NSCLC. Clinically described mechanisms of acquired resistance to KRASG12C inhibitors converge on reactivation of the RAS-MAPK pathway. We hypothesized combining ulixertinib with a KRASG12C inhibitor would circumvent resistance to single agent KRASG12C inhibition, generating increased magnitude and duration of response compared to either single agent alone.

The efficacy of ERK1/2 inhibitor, ulixertinib, in combination with KRASG12C inhibitor, adagrasib, was assessed in cell line derived xenograft models harboring KRASG12C mutations. Models were selected based on response to single agent adagrasib, ranging from sensitive to partially responsive. Combination treatment resulted in superior tumor growth inhibition compared to dosing of either single agent. RNA sequencing was performed on tumor samples that were collected 2 hours after the last dose of treatment. Expression of the mutant KRAS alleles were readily confirmed from RNA sequencing data in all models. Gene expression analysis showed differential expression of MAPK pathway genes in monotherapy versus combination therapy treated groups.

In summary, ulixertinib combined with adagrasib exhibited robust pre-clinical activity in a variety of xenograft models with KRASG12C and should be further evaluated.

Citation Format: Deborah Knoerzer, Anupama Reddy, Jessica A. Box, Anna Groover, Brent Kreider, Martin Teresk, Caroline M. Emery. The combination of ulixertinib (ERK1/2 Inhibitor) and KRASG12C inhibition demonstrates significant efficacy in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2692.

The first-in-class ERK inhibitor ulixertinib shows promising activity in mitogen-activated protein kinase (MAPK)-driven pediatric low-grade glioma models

BACKGROUND

Pediatric low-grade gliomas (pLGG) are the most common pediatric central nervous system tumors, with driving alterations typically occurring in the MAPK pathway. The ERK1/2 inhibitor ulixertinib (BVD-523) has shown promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors.

METHODS

We investigated the antitumoral activity of ulixertinib monotherapy as well as in combination with MEK inhibitors (MEKi), BH3-mimetics, or chemotherapy in pLGG. Patient-derived pLGG models reflecting the two most common alterations in the disease, KIAA1549:BRAF-fusion and BRAFV600E mutation (DKFZ-BT66 and BT40, respectively) were used for in vitro and in vivo (zebrafish embryos and mice) efficacy testing.

RESULTS

Ulixertinib inhibited MAPK pathway activity in both models, and reduced cell viability in BT40 with clinically achievable concentrations in the low nanomolar range. Combination treatment of ulixertinib with MEKi or BH3-mimetics showed strong evidence of antiproliferative synergy in vitro. Ulixertinib showed on-target activity in all tested combinations. In vivo, sufficient penetrance of the drug into brain tumor tissue in concentrations above the in vitro IC50 and reduction of MAPK pathway activity was achieved. In a preclinical mouse trial, ulixertinib mono- and combined therapies slowed tumor growth and increased survival.

CONCLUSIONS

These data indicate a high clinical potential of ulixertinib for the treatment of pLGG and strongly support its first clinical evaluation in pLGG as single agent and in combination therapy in a currently planned international phase I/II umbrella trial.

Phase Ib Study of Ulixertinib Plus Gemcitabine and Nab-Paclitaxel in Patients with Metastatic Pancreatic Adenocarcinoma

BACKGROUND

Ulixertinib is a novel oral ERK inhibitor that has shown promising single-agent activity in a phase I clinical trial that included patients with RAS-mutant cancers.

METHODS

We conducted a phase Ib trial combining ulixertinib with gemcitabine and nab-paclitaxel (GnP) for untreated metastatic pancreatic adenocarcinoma. The trial comprised a dose de-escalation part and a cohort expansion part at the recommended phase II dose (RP2D). Primary endpoint was to determine the RP2D of ulixertinib plus GnP and secondary endpoints were to assess toxicity and safety profile, biochemical and radiographic response, progression-free survival (PFS) and overall survival (OS).

RESULTS

Eighteen patients were enrolled. Ulixertinib 600 mg PO twice daily (BID) with GnP was initially administered but was de-escalated to 450 mg BID as RP2D early during dose expansion due to poor tolerability, which ultimately led to premature termination of the study. Common treatment-related adverse events (TRAEs) were anemia, thrombocytopenia, rash and diarrhea. For 5 response evaluable patients, one patient achieved a partial response and 2 patients achieved stable disease. For 15 patients who received the triplet, median PFS and OS were 5.46 and 12.23 months, respectively.

CONCLUSION

Ulixertinib plus GnP had similar frequency of grade ≥3 TRAEs and potentially efficacy as GnP, however was complicated by a high rate of all-grade TRAEs (ClinicalTrials.gov Identifier: NCT02608229).

Case report: response to the ERK1/2 inhibitor ulixertinib in BRAF D594G cutaneous melanoma

Melanoma is characterized by oncogenic mutations in pathways regulating cell growth, proliferation, and metabolism. Greater than 80% of primary melanoma cases harbor aberrant activation of the mitogen-activated protein kinase kinase/extracellular-signal-regulated kinase (MEK/ERK) pathway, with oncogenic mutations in BRAF, most notably BRAF V600E, being the most common. Significant progress has been made in BRAF-mutant melanoma using BRAF and MEK inhibitors; however, non-V600 BRAF mutations remain a challenge with limited treatment options. We report the case of an individual diagnosed with stage III BRAF D594G-mutant melanoma who experienced an extraordinary response to the ERK1/2 inhibitor ulixertinib as fourth-line therapy. Ulixertinib was obtained via an intermediate expanded access protocol with unique flexibility to permit both single-agent and combination treatments, dose adjustments, breaks in treatment to undergo surgery, and long-term preventive treatment following surgical resection offering this patient the potential for curative treatment.

Abstract 415: The characterization of in vitro models demonstrating a significant delay of acquired resistance to ulixertinib (ERK1/2)

Ulixertinib (BVD-523) is a first-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other anti-cancer therapeutics. Clinical acquired resistance has been described by others for numerous efficacious small molecule agents. Relevant to the MAPK pathway, emergence of resistance to BRAF and MEK inhibitors limits their clinical efficacy.

In vitro models of ulixertinib resistance were generated in an endeavor to characterize and predict potential clinical mechanisms of resistance and guide rational combination therapies. The BRAF-V600E mutant melanoma cell line, A375, was cultured in progressively increasing concentrations of ulixertinib or other MAPK pathway inhibitors (dabrafenib and/or trametinib). Drug-resistant A375 clones were readily obtained following growth in high concentrations of dabrafenib or trametinib. In contrast, developing resistance to ulixertinib proved challenging. Eventually, ulixertinib resistant clones emerged and demonstrated varying degrees of cross-resistance to other MAPK pathway inhibitors and displayed bell-shaped dose-response curves indicative of drug addiction for optimal proliferation. To elucidate potential mechanisms of resistance, Reverse Phase Protein Array profiling of 306 proteins was performed on parental A375 and ulixertinib-resistant clones following treatment with ulixertinib at varying concentrations and treatment times. Principal component analysis revealed clustering of resistant clones by ulixertinib treatment conditions (concentrations and duration). Differences between parental A375 and ulixertinib resistant clones were revealed, including components of MAPK, HER2, and autophagy markers.

This work begins to tease out potential mechanisms of resistance to ulixertinib and guide potential combination partners that could circumvent acquired resistance.

Citation Format: Deborah Knoerzer, Anupama Reddy, David Sorrell, Caroline M. Emery. The characterization of in vitro models demonstrating a significant delay of acquired resistance to ulixertinib (ERK1/2) [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 415.

Abstract 4022: ERK1/2 inhibitor ulixertinib demonstrates activity in atypical (non-V600) BRAF mutant models

Atypical BRAF (non-V600) alterations comprise approximately half of all BRAF mutations in cancer and can be categorized according to characteristics of molecular signaling (either Class II or III). Atypical BRAF alterations are rare (approximately 3% across all human cancers) and there are currently no approved therapies for this indication. As next-generation sequencing becomes standard clinical practice, oncologists are frequently identifying atypical BRAF alterations in their patients’ tumors. The efficacy of the first-in-class ERK1/2 inhibitor, ulixertinib (BVD-523), was assessed across 10 patient-derived xenograft (PDX) models, which harbored class II or III BRAF alterations (5 models with type II alterations, 4 models with class III, and 1 model with both class II and III). Responses ranging from robust regression to moderate tumor growth delay were observed in 9/10 models. RNA sequencing was performed on tumors from the vehicle-treated and ulixertinib-treated groups with three replicates per PDX model. The samples were collected 2 hours after the last dose of treatment. Expression of the mutant BRAF alleles was readily confirmed from RNA-seq data in all PDX models. In addition, gene expression analysis showed differential expression of MAPK pathway genes in responders compared to the non-responders.

In summary, ulixertinib has exhibited strong pre-clinical activity in a variety of patient-derived xenograft models with atypical BRAF alterations. Ulixertinib has FDA fast-track designation for patients with solid tumors, other than CRC, harboring specific BRAF mutations (G469A, L485W, or L597Q) and is currently under clinical evaluation in patients with tumors harboring any atypical BRAF alteration (NCT04488003).

Citation Format: Deborah Knoerzer, Anupama Reddy, Adnan Derti, Caroline M. Emery. ERK1/2 inhibitor ulixertinib demonstrates activity in atypical (non-V600) BRAF mutant models [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 4022.

Abstract 5333: Pancreatic cancer enhances HER2 signaling through DUSP6 to circumvent therapeutic MAPK inhibition

Background: Oncogenic KRAS is present in almost all cases of pancreatic ductal adenocarcinoma (PDAC). However, targeting KRAS or its canonical signaling cascades, especially the mitogen-activated protein kinase (MAPK) pathway, remains clinically unsuccessful. Targeting ERK kinases has recently emerged as a promising therapeutic strategy and combinatorial strategies should be developed.

Aim: Identify adaptive mechanisms to ERK inhibition that can be co-targeted to achieve effective tumor inhibition in multiple patient-derived xenograft (PDX) models.

Methods: Reverse-phase protein array (RPPA) was used in early-passage patient-derived cell lines (PDCLs) to identify potential resistance mechanisms. These were confirmed using RNA interference and overexpression in PDAC cell lines and PDCLs. The promising combinations were tested in 30 early-passaged PDAC PDXs.

Results: RPPA showed dramatic downregulation of DUSP4 and DUSP6 phosphatases following MEK and ERK inhibition, which coincided with upregulation of phospho-HER2 and -HER3. Knockdown of DUSP6, but not DUSP4, was sufficient in phosphorylation of HER2. Conversely, overexpression of DUSP6 curbed HER2 and ERK activation. Downregulation of DUSP4 and DUSP6 induced by ulixertinib, an ERK inhibitor now in clinical development, was reversed by bortezomib, suggesting DUSP4 and DUSP6 are proteosomally degraded. Combined ulixertinib plus PI3K inhibitor copanlisib, or pan-HER inhibitor afatinib slowed but did not arrest PDX tumor growth in vivo, and addition of gemcitabine was required to achieve tumor regression or durable growth arrest. Alternatively, ulixertinib or MEK inhibitor (trametinib) in combination with trastuzumab deruxtecan (DS-8201a), an anti-HER2 conjugated topoisomerase I inhibitor, were extremely effective, leading to complete and durable tumor regression for all tested PDX models. We showed that upregulation of HER2 expression following MEK or ERK inhibitor treatment provides a conduit for enhanced internalization of DS-8201a.

Conclusions: Our study provided novel mechanistic insight on how PDAC cells evade MAPK inhibition via enhancing HER2 signaling. We demonstrated that the combination of MEK or ERK inhibitor plus DS-8201a is extremely effective, leading to complete tumor regression in multiple PDAC PDX models. This combination should be advanced as a clinical trial for PDAC patients.

Keys: DS-8201a, DUSP6, HER2, KRAS, ulixertinib, pancreatic ductal adenocarcinoma

Citation Format: Ashenafi Shiferaw Bulle, Kuljeet Seehar, Sapana Bansod, Yali Chen, Chen Hung-Po, Paarth B. Dodhiawala, Lin Li, Vikas Somani, Jacqueline Mudd, Ryan C. Fields, Deborah Knoerzer, Andrea Wang-Gillam, Lim Kian-Huat. Pancreatic cancer enhances HER2 signaling through DUSP6 to circumvent therapeutic MAPK inhibition [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 5333.

Abstract 5221: The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics

Ulixertinib (BVD-523) is a well-tolerated, orally delivered, catalytic ERK1/2 inhibitor, which has shown promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors. Pediatric low grade gliomas (pLGGs) are the most common pediatric brain tumors, with the most frequent driving alterations (KIAA:BRAF fusion, BRAF V600E mutation) occurring in the MAPK pathway.

To investigate the anti-tumoral activity of ulixertinib in pLGG, cell lines recapitulating both main MAPK alterations were used: DKFZ-BT66 (pilocytic astrocytoma; KIAA:BRAF fusion) and BT40 (pleomorphic xanthoastrocytoma; BRAF V600E mutation and CDKN2A/B deletion). The potential synergism of combinations with MEK inhibitors, senolytics, and chemotherapy was investigated in vitro using metabolic activity and MAPK activity assays. The most promising combinations were validated in vitro by analysis of viable, dead, and apoptotic cells through high-content microscopy. The most clinically relevant combinations were further validated in vivo: 1) in two zebrafish embryo models (respectively, BT40 and DKFZ-BT66 yolk sac injection) and 2) in NSG mice (BT40 orthotopic PDX) including in vivo pharmacokinetic and -dynamic analyses.

Our data demonstrate ulixertinib’s ability to inhibit MAPK pathway activity in all used models. Ulixertinib treatment reduced cell viability in the BRAF V600E mutated cell line at a remarkably low concentration of 62.7 nM (compared to other cell lines’ IC50 from the Genomics of Drug Sensitivity in Cancer database). In vivo pharmacokinetic and -dynamic analyses showed good penetrance of the drug into mouse brain tissue, with concentrations above the in vitro IC50 and reduction of MAPK activity as assessed by Western blot. Furthermore, ulixertinib treatment slowed tumor growth and significantly increased survival in NSG mice with orthotopic BT40 xenografts.

Ulixertinib showed indications for anti-proliferative synergy in vitro, according to the Loewe and Bliss independence models, in combination with MEK inhibitors (trametinib, binimetinib) or senolytics (navitoclax, A1331852). Combinations with chemotherapy (carboplatin, vinblastine) were at most additive. Indications for synergy with binimetinib and navitoclax were confirmed in the zebrafish embryo xenograft models for both MAPK-altered backgrounds. The combination of ulixertinib with navitoclax was further investigated in the BT40 PDX mouse model, where tumor growth and survival were comparable to ulixertinib monotherapy.

In conclusion, our data indicate a strong potential for ulixertinib as a clinically relevant therapeutic option for the treatment of pLGG to be further investigated in upcoming clinical trials. Potential synergism with MEK inhibitors and senolytics was noted and warrants further investigation.

Citation Format: Romain Sigaud, Lisa Rösch, Charlotte Gatzweiler, Julia Benzel, Laura von Soosten, Heike Peterziel, Sara Najafi, Simay Ayhan, Nina Hofmann, Kathrin I. Förster, Jürgen Burhenne, Rémi Longuespée, Cornelis M. van Tilburg, David T. Jones, Stefan M. Pfister, Deborah Knoerzer, Brent Kreider, Max Sauter, Kristian W. Pajtler, Marc Zuckermann, Ina Oehme, Olaf Witt, Till Milde. The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics [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 5221.

Abstract 404: Identification of combination partners to combat acquired resistance to ulixertinib (ERK1/2 inhibitor) using transcriptomics

Drug resistance is arguably the rate-limiting step in the successful clinical utility of MAPK inhibitors. Several mechanisms of resistance to BRAF and MEK inhibitors have been proposed, including feedback mechanisms and activation of complementary signaling pathways, which have led to the development of combination therapies. Ulixertinib (BVD-523), a first-in-class and ERK1/2 inhibitor, is clinically effective in patients with tumors harboring alterations in the MAPK pathway. In this project, we have developed resistance clones to ulixertinib and have identified mechanisms of acquired resistance using RNA-seq analysis, thus enabling us to identify potential combination partners to combat resistance.

In vitro experiments were deployed to develop resistance models to ulixertinib. Resistance clones were developed by culturing A375 cell line (melanoma; BRAF V600E) in escalating concentrations of ulixertinib.

RNA-sequencing was performed on the parental model and the resistance clones following varying treatment conditions with ulixertinib. RNAseq and principal component analysis revealed strong differences between parental and resistance clones, with further differentiation between acute high concentration and chronic treatment models compared to models treated with acute, lower concentrations of ulixertinib. These results highlight the presence of a dose-dependent resistance phenotype. Differential gene expression analysis revealed enrichment of several pathways, including MAPK, autophagy, focal adhesion, JAK/STAT, and VEGF. Interestingly, we observed rewiring of PI3K/AKT by shifting the signaling from EGFR to ERBB2 in the resistance models. The magnitude of changes in these genes and pathways also exhibited a dose-dependent effect, with higher concentration models showing a higher fold-change compared to the lower concentration models. We explored these hypotheses by performing combination experiments with ulixertinib in the generated resistance clones. Synergistic combination targets in the ulixertinib resistance clones included ERBB2, and FAK. We also validated combinations with autophagy inhibitors, one of which is now being tested in a Phase I clinical trial (NCT04145297).

In summary, we have identified some potential resistance mechanisms to ulixertinib and have validated key genes/pathways which may act as synergistic combination targets. This work not only informs future clinical development for ulixertinib but also improves our understanding of the complex interplay between the MAPK and other signaling pathways.

Citation Format: Anupama Reddy, David Sorrell, Deborah Knoerzer, Caroline M. Emery. Identification of combination partners to combat acquired resistance to ulixertinib (ERK1/2 inhibitor) using transcriptomics [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 404.

Abstract 1057: Significant efficacy demonstrated with the combination of ulixertinib (ERK1/2 inhibitor) and CDK4/6 inhibitors in MAPK altered models

Ulixertinib (BVD-523) is a first-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other anti-cancer therapeutics. Palbociclib and ribociclib are FDA approved orally active, potent, and highly selective reversible inhibitors of the CDK4 and CDK6 kinases. As it is well established that ERK activation increases cyclin D levels and entry into the cell cycle, we hypothesized that the combination of ERK1/2 and CDK4/6 inhibition would have synergistic antitumor activity and cause tumor regression in vivo.

Initial in vitro work combined ulixertinib with CDK4/6 inhibitors across a small panel of lung cancer cell lines. Cell lines carrying a KRAS mutation were more sensitive to ulixertinib relative to KRAS wild type cell lines based on single agent IC50 values. The single agent IC50 values for the CDK4/6 inhibitors were dependent on whether a metabolic or non-metabolic readout for cell viability was used. The combination interactions across a dose matrix of concentrations were determined by the Loewe Additivity and Bliss Independence models. The results of combining ulixertinib and CDK4/6 inhibitors ranged from additive to potentially synergistic.

The combination of ulixertinib and palbociclib was then assessed against four xenograft models representing colorectal, melanoma, and pancreatic tumor types, each harboring an alteration within a component of the MAPK pathway. Palbociclib monotherapy across all models showed limited tumor growth inhibition (TGI) while ulixertinib monotherapy demonstrated modest TGI across all models. The combination groups demonstrated significant responses ranging from 75% - 90% TGIs. All treatment regimens were well tolerated across all models. Downstream assays were completed including reverse phase protein arrays (RPPA). Using RPPA, treatment effects on protein signaling was evaluated in the MAPK family, cell cycle regulation, and other associated feedback and compensatory pathways. Notably, suppression of protein targets downstream of ERK1/2 were seen with both ulixertinib monotherapy and combination therapy. Similarly, the combination therapy group reduced protein levels involved in cell cycle progression, which was not seen in either monotherapy group alone.

The efficacy demonstrated with this preclinical work has proven to be translatable to the clinic as the combination of ulixertinib and palbociclib recently achieved MTD in a Phase I trial in advanced solid tumors including pancreatic cancer (NCT 03454035).

Citation Format: Caroline M. Emery, Brian Corgiat, Justin Davis, David Sorrell, Mitch Johnson, Brent Kreider, Deborah Knoerzer. Significant efficacy demonstrated with the combination of ulixertinib (ERK1/2 inhibitor) and CDK4/6 inhibitors in MAPK altered models [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 1057.

LGG-25. The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics

Ulixertinib (BVD-523) is a catalytic ERK1/2 inhibitor that showed promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors. Pediatric low-grade gliomas (pLGG) are the most common pediatric brain tumors, with the most frequent driving alterations in the MAPK pathway. The anti-tumor activity of ulixertinib in pLGG and its potential synergism in combination with MEK inhibitors, senolytics, and chemotherapy were investigated in vitro using metabolic activity, MAPK reporter assay and high-content microscopy in pLGG-derived cell lines (DKFZ-BT66 - KIAA:BRAF fusion; BT40 - BRAF V600E mutation and CDKN2A/B deletion). The most clinically relevant combinations were further validated in vivo: 1) in zebrafish embryo models (BT40 and DKFZ-BT66 yolk sac injection) and 2) in NSG mice (BT40 orthotopic PDX) including in vivo pharmacokinetic and -dynamic analyses. Ulixertinib inhibited MAPK pathway activity in all models and reduced cell viability in the BRAF V600E mutated cell line at concentrations in the nanomolar range. In vivo pharmacokinetic and -dynamic analyses showed penetrance of the drug into mouse brain tissue and on-target activity, with concentrations above the in vitro IC50 and reduction of MAPK activity. Ulixertinib treatment slowed tumor growth and significantly increased survival in NSG mice with BT40 xenografts. Ulixertinib showed indications for anti-proliferative synergy in vitro in combination with MEK inhibitors (trametinib, binimetinib) or BH3 mimetics (navitoclax, A-1331852). Combinations with chemotherapy (carboplatin, vinblastine) were at most additive. Indications for synergy with binimetinib and navitoclax were confirmed in the zebrafish embryo models. In the NSG mouse model, the combination of ulixertinib with senolytics induced effects on tumor growth and survival comparable to ulixertinib monotherapy. Ulixertinib shows promising potential as a clinically relevant therapeutic option for the treatment of pLGG to be further investigated in upcoming clinical trials. Potential synergism with MEK inhibitors and BH3 mimetics was noted and warrants further investigation.

Real-time Genomic Characterization of Advanced Pancreatic Cancer to Enable Precision Medicine

Clinically relevant subtypes exist for pancreatic ductal adenocarcinoma (PDAC), but molecular characterization is not yet standard in clinical care. We implemented a biopsy protocol to perform time-sensitive whole-exome sequencing and RNA sequencing for patients with advanced PDAC. Therapeutically relevant genomic alterations were identified in 48% (34/71) and pathogenic/likely pathogenic germline alterations in 18% (13/71) of patients. Overall, 30% (21/71) of enrolled patients experienced a change in clinical management as a result of genomic data. Twenty-six patients had germline and/or somatic alterations in DNA-damage repair genes, and 5 additional patients had mutational signatures of homologous recombination deficiency but no identified causal genomic alteration. Two patients had oncogenic in-frame BRAF deletions, and we report the first clinical evidence that this alteration confers sensitivity to MAPK pathway inhibition. Moreover, we identified tumor/stroma gene expression signatures with clinical relevance. Collectively, these data demonstrate the feasibility and value of real-time genomic characterization of advanced PDAC.Significance: Molecular analyses of metastatic PDAC tumors are challenging due to the heterogeneous cellular composition of biopsy specimens and rapid progression of the disease. Using an integrated multidisciplinary biopsy program, we demonstrate that real-time genomic characterization of advanced PDAC can identify clinically relevant alterations that inform management of this difficult disease. Cancer Discov; 8(9); 1096-111. ©2018 AACR.See related commentary by Collisson, p. 1062This article is highlighted in the In This Issue feature, p. 1047.

Abstract B085: Preclinical pharmacokinetic/pharmacodynamic (PK/PD) relationship demonstrated for BVD-723, a potent and selective phosphoinositide 3-kinase gamma (PI3Kγ) inhibitor

The phosphoinositide 3-kinase (PI3K) family of enzymes play a pivotal role in controlling vital cellular functions, including proliferation, motility, glucose metabolism, and survival. The PI3Kγ isoform has been shown to play an important role in immune cell migration and function in the tumor microenvironment. BVD-723 is a potent and selective small-molecule inhibitor of the PI3Kγ isoform (PI3K γ/α/β/δ Ki = 8/280/220/160 nM). AKT, a serine/threonine protein kinase, is a downstream effector of PI3K. AKT phosphorylation was therefore chosen as a PD marker to demonstrate BVD-723 activity. Here we describe the PK/PD relationship from a single-day, oral, multi-dose level, multi-timepoint study in Balb/c mice. The PD assay, utilizing phospho flow cytometry, measured the ability of BVD-723 to attenuate AKT phosphorylation at the S473 residue in response to extracellular ligands in primary cell subsets that included monocytes, T cells, and B cells. Initial work identified CCL2 and CXCL12, which are thought to signal primarily through PI3Kγ, as ligands that induced robust pAKT signal in both human and murine monocytes. LPS, which is thought to signal primarily through PI3Kδ, was used to assess isoform selectivity in this assay. BVD-723 was administered as a single oral dose (0.5, 1, 3, 5, 10, 30, or 100 mg/kg) to Balb/c female mice. Blood was collected via terminal draw from 3 animals per dose group and per timepoint (pre-dose, 0.5, 1, 2, 4, 6, 8, 12, and 24 hours) and was split into two samples. The first sample was processed to plasma and BVD-723 levels measured using LC-MS/MS assay. The second whole blood sample was analyzed for pAKT following ex vivo stimulation. PK analysis of each dose demonstrated a Tmax between 2-6 hours and a t1/2 of 4-5 hours. The Cmax levels for each dose of 0.5, 1, 3, 5, 10, 30, and 100 mg/kg were 218, 577, 2050, 3670, 9130, 23200, and 29300 ng/ml, respectively, and the AUC0-24 values were 1.8, 5, 21, 38.2, 107, 318, and 519 µg*hr/ml, respectively. The PD assay demonstrated a clear dose- and time-dependent inhibition of AKT phosphorylation in monocytes downstream of CCL2 and CXCL12 stimulation but not LPS stimulation. Consistent with the PK data, a peak inhibition of pAKT signal occurred between 2-4 hours post dose. The CXCL12-induced AKT phosphorylation in monocytes was robustly inhibited for 24 hours at 30 mg/kg and 100 mg/kg. Overall, the PD results showed clear selectivity of BVD-723 for PI3Kγ inhibition in monocytes, with no inhibition of PI3Kδ. Additional ex vivo studies in blood were conducted utilizing this PD assay comparing other PI3K isoform selective inhibitors to BVD-723. These data provide a solid PK/PD relationship, providing guidance for continued development of BVD-723 for oncology.

Citation Format: Deborah Knoerzer, Martin Teresk, Peter Krutzik, Erika O’Donnell, Gary DeCrescenzo, Dean Welsch, Caroline Emery. Preclinical pharmacokinetic/pharmacodynamic (PK/PD) relationship demonstrated for BVD-723, a potent and selective phosphoinositide 3-kinase gamma (PI3Kγ) inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B085.

Esomeprazole MUPS 40 mg tablets and esomeprazole MUPS 40 mg tablets encapsulated in hard gelatine are bioequivalent

OBJECTIVE

To investigate the bioequivalence of esomeprazole MUPS 40 mg tablets administered with and without a hard gelatine capsule.

MATERIAL AND METHODS

Bioequivalence of the esomeprazole MUPS 40 mg tablet administered without (Reference) and with a hard gelatine capsule (Test) was evaluated using a randomized, two-period crossover study. In each study period 49 healthy male Caucasian subjects received a single oral dose of 40 mg esomeprazole. Blood samples were collected at specified time intervals, and serum was separated and analyzed for esomeprazole concentrations using a validated HPLC-MS method. The primary parameters were AUC (extent of absorption) and Cmax (rate of absorption). The time-to-peak plasma concentration, tmax, and the elimination half-life, t1/2, were determined as secondary characteristics. Point estimates and 90%-confidence intervals were obtained for the ratio of the population medians of Test and Reference, using a multiplicative model and a parametric analysis except in the case of tmax, where an additive model and a non-parametric analysis was used. Bioequivalence of Test and Reference was concluded if the 90%-confidence intervals were entirely within the predefined equivalence ranges.

RESULTS

The AUC(0-infinity) and Cmax-ratios (Test/Reference) were 1.00 and 1.01, respectively. The 90%-confidence intervals for AUC(0-infinity) (0.94-1.06) and Cmax (0.93-1.09) of these ratios were within the predefined equivalence range of 0.80-1.25 and 0.75-1.33, respectively. The ratios and 90%-confidence intervals of the secondary characteristics t1/2 and tmax were also within the respective predefined equivalence ranges. Both esomeprazole formulations were well tolerated and safe.

CONCLUSION

The encapsulation of esomeprazole MUPS 40 mg tablets does not influence the extent and rate of absorption assessed by using AUC(0-infinity) and Cmax. Thus, bioequivalence could be demonstrated.