Combination Of Selumetinib Research Articles

In vitro inhibitory effects of selumetinib on activity of human UDP-glucuronosyltransferases and prediction of in vivo drug-drug interactions

Selumetinib is an oral, effective, and selective tyrosine kinase inhibitor targeting mitogen-activated protein kinase 1 and 2 (MEK1/2), which is clinically active in multiple tumor types, such as neurofibromatosis type 1 (NF1), melanoma, gliomas and non-small cell lung cancer (NSCLC). The purpose of this article was to assess the effects of selumetinib on the activities of twelve human UDP-glucosyltransferases (UGTs) including UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, and 2B17, and its potential for inducing clinical drug-drug interactions (DDIs). The results demonstrated that selumetinib potently inhibited the activity of UGT2B7 through the mechanism of mixed inhibition with the inhibition constant value of 5.79 ± 0.65 μM. Furthermore, the plasma concentration of UGT2B7 substrate as the co-administered drug was predicted to be increased by at least 84 % when patients took selumetinib 75 mg twice daily, suggesting a high potential to induce clinical DDIs. Selumetinib exhibited weak inhibitory effects on other human UGTs and was unlikely to trigger off UGTs-mediated DDIs except for UGT2B7. Therefore, the combination of selumetinib with the substrate drug of UGT2B7 requires additional attention to avoid adverse events in clinical treatment.

Selumetinib overcomes gefitinib primary and acquired resistance by regulating MIG6/STAT3 in NSCLC.

Gefitinib, as the first-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), has achieved great advances in the treatment of non-small cell lung cancer (NSCLC), but drug resistance will inevitably occur. Therefore, exploring the resistance mechanism of gefitinib and developing new combination treatment strategies are of great importance. In our study, the results showed that selumetinib (AZD6244) synergistically inhibited the proliferation of NSCLC with gefitinib. Selumetinib also enhanced gefitinib-induced apoptosis and migration inhibition ability in gefitinib-resistant lung cancer cell lines. Subsequently, the negative regulation between MIG6 and STAT3 was observed and verified through the STRING database and western blotting assays. Sustained activation of STAT3 was significantly downregulated when co-treatment with selumetinib in gefitinib-resistant cells. However, the downregulation of p-STAT3, resulting from the combination of selumetinib and gefitinib was counteracted by the deletion of MIG6, suggesting that selumetinib enhanced gefitinib sensitivity by regulating MIG6/STAT3 in NSCLC. In contrast, p-STAT3 was further inhibited after treatment with gefitinib and selumetinib when MIG6 was overexpressed. Furthermore, the combined administration of selumetinib and gefitinib effectively promoted the sensitivity of lung cancer xenografts to gefitinib in vivo, and the tumor inhibition rate reached 81.49%, while the tumor inhibition rate of the gefitinib monotherapy group was only 31.95%. Overall, MIG6/STAT3 negative regulation plays an important role in the sustained activation of STAT3 and the resistance to EGFR-TKIs. Our study also suggests that EGFR-TKIs combined with MEK1/2 inhibitors, such as selumetinib, may be beneficial to those NSCLC patients who develop a primary or acquired resistance to EGFR-TKIs, providing theoretical support for combining TKIs and selumetinib in clinical cancer treatment.

The MEK Inhibitor Selumetinib in Combination with Dexamethasone Leads to Responses in Adult and Pediatric Patients with Relapsed RAS-Pathway Mutated Acute Lymphoblastic Leukemia: Results of a Phase 1/2 Study

Introduction Relapsed acute lymphoblastic leukemia (ALL) is a major therapeutic challenge and novel treatment strategies are urgently sought. RAS-pathway activating mutations are found in 38% of relapsed pediatric B-cell precursor (BCP) ALL patients ( J Irving, Blood, 2014). Additional mutations that activate the RAS-signalling cascade (NF1, BRAF, IKZF2, IKZF3, JAK1) have also been found with varying frequencies in relapsed ALL. Selumetinib, a potent MEK1/2 inhibitor, works synergistically with dexamethasone in mouse models of RAS-pathway mutated ALL by enhanced upregulation of the proapoptotic protein, BIM ( EC Matheson, Haematologica, 2019). Methods We conducted an international, parallel cohort, dose-finding and expansion trial to evaluate the combination of selumetinib with dexamethasone in adult and pediatric patients with relapsed/refractory T- or BCP-ALL harbouring RAS-pathway activating mutations. Selumetinib was supplied free of charge by AstraZeneca. Details of in-/exclusion criteria, treatment and dosages are described by T. Menne, BMJ open, 2022. The trial was conducted according to the Declaration of Helsinki and after medical ethics committees of participating countries had approved the protocol. The trial was registered under NCT03705507 and ISRCTN92323261 and sponsored by the University of Birmingham. Results The trial opened to recruitment on 17-Apr-2018, the first patient was recruited on 18-May-2018. Twelve patients were included, 8 adults and 4 children. Six of the 8 adult patients had relapsed/refractory T-ALL, the remaining patients had BCP-ALL. Further patient characteristics are summarized in table 1. Pharmacokinetic measurements demonstrated lower maximum concentrations for pediatric patients on dose level -1, and no significant effect of CYP3A4 induction was observed. A total of 561 Adverse Events (AEs) were reported for 11/12 patients. For 1 patient who died on day 3 of treatment due to leukemia related events, no AEs were reported. 3/11 patients (27%) had AEs of a maximum grade 1-3, 5 patients (45%) had a maximum AE grade 4, and 3 patients (27%) suffered a grade 5 AE (2x sepsis, pneumonia). Further details of AEs are depicted in table 2. Sixteen serious adverse events (SAEs) were observed in 9 patients. Of those, 11 were due to infection, and all 9 patients had an SAE involving infection, most frequently neutropenic fever or sepsis. Three SAEs were fatal: one concerned a child with sepsis who had stopped trial treatment 14 days previously. Two patients were adults: one became septic 2 days after being admitted for myopathy/weakness and collapsed shortly after starting antibiotics. The 2 nd patient was admitted with fever, diagnosed with pneumonia and died 5 days later of cardiac arrest. All fatal events occurred before the last of 3 urgent safety measures were implemented in September 2019, changing the continuous dexamethasone dosing to pulsed doses and mandating antimicrobial prophylaxis. The 5 non-infection SAEs were anaemia, constipation, myopathy/weakness, fatigue and heart failure. Response data are available for 9/12 patients. Two patients died before reaching the 1 st bone marrow assessment after 28 days, and 1 patient stopped trial treatment after 11 days. Of the remaining 9 patients, 5 were non-responders (56%) and 4 (44%) had a complete remission (CR), or a CR with incomplete platelet recovery (3 adults, 1 child; response rate 44%). Of the 4 patients in CR, 2 adults had relapsed T-ALL and stayed on treatment for 3 to almost 5 months. Of the responding BCP-ALL patients, 1 patient died of pneumonia in cycle 2, and 1 pediatric patient progressed after cycle 2 then discontinued. Conclusion Recruitment to the trial was unexpectedly slow, due to competing new treatment options (commercial CAR-T cells, blinatumomab, inotuzumab), delays in opening international centres and recruitment stops due to COVID. Initially, the trial suffered from frequent SAEs concerning infections, which lead to a total of 3 urgent safety measures in 2018 and 2019, including lowering the dose of dexamethasone in the 2 nd half of cycle 1, mandating fluoroquinolone and co-trimoxazole prophylaxis and finally changing continuous dexamethasone to pulses. The response data with 44% of patients achieving a CR is promising and will need to be further evaluated in the context of targeted treatment approaches for RAS-altered leukemias, especially for relapsed T-ALL.

A phase I study of MEK inhibitor selumetinib in combination with azacitidine in patients with higher-risk chronic myeloid neoplasia.

TPS7084 Background: Myelodysplastic syndrome (MDS), Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), and MDS/MPN overlap syndromes present significant clinical challenges for patients deemed transplant ineligible, and who are relapsed or refractory to conventional therapies. RAS-pathway activating mutations in myeloid malignancies are associated with a proliferative phenotype and contribute to disease progression. Cooperation between RAS-dependent signaling and epigenetic dysregulation provides the basis for rationally designed combination studies. Selumetinib (AZD6244) is a potent, selective, orally bioavailable, and non-ATP competitive small molecule inhibitor of MEK1/2, downstream of RAS. Methods: This is an investigator-initiated, Phase I, open-label dose-escalation study of selumetinib in combination with azacitidine for patients with higher risk MDS, MDS/MPNs, and myelofibrosis. The trial will enroll patients with high-risk myeloid neoplasms that meet disease-specific criteria for MDS or MPNs and who require treatment. This phase I study follows a 3+3 dose-escalation design, with three planned dose levels across two different cohorts (A and B). The dose of azacitidine 75 mg/m2 will remain stable, with three planned selumetinib dose levels (50 mg, 75 mg, and 100mg, respectively) across the two cohorts. Azacitidine will be given on days 1-7 followed by selumetinib from days 7-21 of 28 day cycles. Cohort A includes subjects with MDS with relapsed/refractory disease requiring therapy and MDS/MPN overlap syndromes; Cohort B includes subjects with myelofibrosis refractory or intolerant to JAK inhibitor therapy or ineligible for ruxolitinib treatment given baseline cytopenias (thrombocytopenia < 50,000/uL, anemia < 9 g/dL, and/or red cell transfusion dependent). The trial has an enrollment goal of 18 to 24 subjects, and treatment will continue indefinitely if the patient continues to derive benefit. Dose escalation will proceed independently within both cohorts. Cohort A is nearing completion of enrollment and cohort B is actively enrolling. The primary objective is to determine the maximum tolerated dose of selumetinib in combination with azacitidine. Select secondary and exploratory objectives include describing the preliminary clinical response rates and observing relationships between the presence of RAS activating mutations, RAS pathway activation, and clinical response. Clinical trial information: NCT03326310 .

Combining SOS1 and MEK Inhibitors in a Murine Model of Plexiform Neurofibroma Results in Tumor Shrinkage.

Individuals with neurofibromatosis type 1 develop rat sarcoma virus (RAS)-mitogen-activated protein kinase-mitogen-activated and extracellular signal-regulated kinase (RAS-MAPK-MEK)-driven nerve tumors called neurofibromas. Although MEK inhibitors transiently reduce volumes of most plexiform neurofibromas in mouse models and in neurofibromatosis type 1 (NF1) patients, therapies that increase the efficacy of MEK inhibitors are needed. BI-3406 is a small molecule that prevents Son of Sevenless (SOS)1 interaction with Kirsten rat sarcoma viral oncoprotein (KRAS)-GDP, interfering with the RAS-MAPK cascade upstream of MEK. Single agent SOS1 inhibition had no significant effect in the DhhCre;Nf1 fl/fl mouse model of plexiform neurofibroma, but pharmacokinetics (PK)-driven combination of selumetinib with BI-3406 significantly improved tumor parameters. Tumor volumes and neurofibroma cell proliferation, reduced by MEK inhibition, were further reduced by the combination. Neurofibromas are rich in ionized calcium binding adaptor molecule 1 (Iba1)+ macrophages; combination treatment resulted in small and round macrophages, with altered cytokine expression indicative of altered activation. The significant effects of MEK inhibitor plus SOS1 inhibition in this preclinical study suggest potential clinical benefit of dual targeting of the RAS-MAPK pathway in neurofibromas. SIGNIFICANCE STATEMENT: Interfering with the RAS-mitogen-activated protein kinase (RAS-MAPK) cascade upstream of mitogen activated protein kinase kinase (MEK), together with MEK inhibition, augment effects of MEK inhibition on neurofibroma volume and tumor macrophages in a preclinical model system. This study emphasizes the critical role of the RAS-MAPK pathway in controlling tumor cell proliferation and the tumor microenvironment in benign neurofibromas.

Combined MEK and JAK/STAT3 pathway inhibition effectively decreases SHH medulloblastoma tumor progression

Medulloblastoma (MB) is the most common primary malignant pediatric brain cancer. We recently identified novel roles for the MEK/MAPK pathway in regulating human Sonic Hedgehog (SHH) MB tumorigenesis. The MEK inhibitor, selumetinib, decreased SHH MB growth while extending survival in mouse models. However, the treated mice ultimately succumbed to disease progression. Here, we perform RNA sequencing on selumetinib-treated orthotopic xenografts to identify molecular pathways that compensate for MEK inhibition specifically in vivo. Notably, the JAK/STAT3 pathway exhibits increased activation in selumetinib-treated tumors. The combination of selumetinib and the JAK/STAT3 pathway inhibitor, pacritinib, further reduces growth in two xenograft models and also enhances survival. Multiplex spatial profiling of proteins in drug-treated xenografts reveals shifted molecular dependencies and compensatory changes following combination drug treatment. Our study warrants further investigation into MEK and JAK/STAT3 inhibition as a novel combinatory therapeutic strategy for SHH MB.

Abstract 4024: Combining selumetinib with BH3 mimetics enhances activity in MAPK-activated acute myeloid leukemia

Abstract Mitogen-activated protein kinase (MAPK) pathway alterations comprise some of the most frequent mutations in newly diagnosed acute myeloid leukemia (AML). Moreover, MAPK pathway alterations are also emerging as potential mechanisms of resistance to targeted therapy in AML including FLT3 inhibitors and venetoclax. In an ex vivo pharmacologic analysis of primary AML samples, sensitivity to the MEK inhibitor selumetinib (ARRY-142886) was enriched in patient samples resistant to venetoclax. Clinical activity of MAPK pathway inhibitors such as selumetinib has been explored in AML but monotherapy responses were modest. Another MEK inhibitor, cobimetinib, is currently being tested in combination with venetoclax in AML. We sought to understand whether combining selumetinib with BH3 mimetics such as venetoclax would improve efficacy in AML models. We evaluated combination activity of selumetinib plus venetoclax or the MCL1 inhibitor AZD5991 in a panel of AML cell lines. Cells were exposed to a 6x6 matrix of both agents for 72hrs and then viability assessed using CellTiter-Glo. Combination benefit was assessed using highest single agent (HSA) analysis. Selumetinib+AZD5991 demonstrated strong combination benefit (HSA score >0.1, Emax >0.5) in 4/19 AML cell lines. Selumetinib+venetoclax showed strong combination activity in 6/19 lines. Three lines showed benefit with both combinations. Many of these cell lines harbor MAPK pathway mutations including OCI-AML5 (SOS1N233Y, NF1K1385R), ML-2 (KRASA146T), HL-60 (NRASQ61L), and Nomo-1 (KRASG13D). Selumetinib treatment also led to robust BIM induction in vitro. Nomo-1 xenografts were evaluated for in vivo sensitivity to venetoclax (100 mg/kg qd PO), 5-azacytidine (1mg/kg BID q8h 3days on/4days off IP), AZD5991 (30mpk bid q2h qw IV), selumetinib (10 mg/kg bid q8h PO), as well as combinations of venetoclax+5-aza, AZD5991+selumetinib, and venetoclax+selumetinib. Venetoclax and venetoclax+5-aza treatment were ineffective. Selumetinib monotherapy led to 63% tumor growth inhibition (TGI) but tumors eventually grew out through treatment. The combination of selumetinib+venetoclax slightly improved efficacy (81% TGI) but markedly delayed tumor outgrowth (selumetinib monotherapy arm reached mean tumor volume >1000 mm3 on day 17, selumetinib+venetoclax reached average of ~966 mm3 on day 28). Reducing venetoclax dose (30mg/kg qd) or frequency (100mg/kg 3days on/4days off) maintained most of the combination efficacy. Selumetinb+AZD5991 also strongly improved efficacy compared to either monotherapy (88% TGI, mean tumor volume did not exceed ~400mm3 by day 28). Together these data suggest potential for combining MEK inhibitors with BH3 mimetics in AML. Work is ongoing to further understand how scheduling impacts combination efficacy, evaluate the triple combination of selumetinib+BH3 mimetic+azacytidine, and assess efficacy in disseminated models. Citation Format: Courtney L. Andersen, Azadeh Cheraghchi-Bashi, Patricia Jaaks, Elizabeth A. Coker, Kathleen Burke, Justin Cidado, Paul Smith, Corinne Reimer, Raoul Tibes, Mathew Garnett, Jerome Mettetal. Combining selumetinib with BH3 mimetics enhances activity in MAPK-activated acute myeloid leukemia [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 4024.

Combination of Selumetinib and Radioactive Iodine Therapy Did Not Improve Outcomes in a Phase 3 Trial of High-Risk Differentiated Thyroid Cancer

Combination of Selumetinib and Radioactive Iodine Therapy Did Not Improve Outcomes in a Phase 3 Trial of High-Risk Differentiated Thyroid Cancer

Phase I trial of the MEK inhibitor selumetinib in combination with thoracic radiotherapy in non-small cell lung cancer

BackgroundThe RAS/RAF/MEK/ERK signalling pathway has a pivotal role in cancer proliferation and modulating treatment response. Selumetinib inhibits MEK and enhances effects of radiotherapy in preclinical studies. Patients and methodsSingle-arm, single-centre, open-label phase I trial. Patients with stage III NSCLC unsuitable for concurrent chemo-radiotherapy, or stage IV with dominant thoracic symptoms, were recruited to a dose-finding stage (Fibonacci 3 + 3 design; maximum number = 18) then an expanded cohort (n = 15). Oral selumetinib was administered twice daily (starting dose 50 mg) commencing 7 days prior to thoracic radiotherapy, then with radiotherapy (6–6.5 weeks; 60–66 Gy/30–33 fractions). The primary objective was to determine the recommended phase II dose (RP2D) of selumetinib in combination with thoracic radiotherapy. Results21 patients were enrolled (06/2010–02/2015). Median age: 62y (range 50–73). M:F ratio 12(57%):9(43%). ECOG PS 0:1, 7(33%):14(67%). Stage III 16(76%); IV 5(24%). Median GTV 64 cm3 (range 1–224 cm3). 15 patients comprised the expanded cohort at starting dose. All 21 patients completed thoracic radiotherapy as planned and received induction chemotherapy. 13 (62%) patients received the full dose of selumetinib.In the starting cohort no enhanced radiotherapy-related toxicity was seen. Two patients had dose-limiting toxicity (1x grade 3 diarrhoea/fatigue and 1x pulmonary embolism). Commonest grade 3–4 adverse events: lymphopaenia (19/21 patients) and hypertension (7/21 patients). One patient developed grade 3 oesophagitis. No patients developed grade ≥3 radiation pneumonitis. Two patients were alive at the time of analysis (24 and 26 months follow-up, respectively). Main cause of first disease progression: distant metastases ± locoregional progression (12/21 [57.1%] patients). Six patients had confirmed/suspected pneumocystis jiroveci pneumonia. ConclusionWe report poor outcome and severe lymphopenia in most patients treated with thoracic radiotherapy and selumetinib at RP2D in combination, contributing to confirmed/clinically suspected pneumocystis jiroveci pneumonia. These results suggest that this combination should not be pursued in a phase II trial.ClinicalTrials.gov reference: NCT01146756.

AZD0364 Is a Potent and Selective ERK1/2 Inhibitor That Enhances Antitumor Activity in KRAS-Mutant Tumor Models when Combined with the MEK Inhibitor, Selumetinib.

The RAS-regulated RAF-MEK1/2-ERK1/2 (RAS/MAPK) signaling pathway is a major driver in oncogenesis and is frequently dysregulated in human cancers, primarily by mutations in BRAF or RAS genes. The clinical benefit of inhibitors of this pathway as single agents has only been realized in BRAF-mutant melanoma, with limited effect of single-agent pathway inhibitors in KRAS-mutant tumors. Combined inhibition of multiple nodes within this pathway, such as MEK1/2 and ERK1/2, may be necessary to effectively suppress pathway signaling in KRAS-mutant tumors and achieve meaningful clinical benefit. Here, we report the discovery and characterization of AZD0364, a novel, reversible, ATP-competitive ERK1/2 inhibitor with high potency and kinase selectivity. In vitro, AZD0364 treatment resulted in inhibition of proximal and distal biomarkers and reduced proliferation in sensitive BRAF-mutant and KRAS-mutant cell lines. In multiple in vivo xenograft models, AZD0364 showed dose- and time-dependent modulation of ERK1/2-dependent signaling biomarkers resulting in tumor regression in sensitive BRAF- and KRAS-mutant xenografts. We demonstrate that AZD0364 in combination with the MEK1/2 inhibitor, selumetinib (AZD6244 and ARRY142886), enhances efficacy in KRAS-mutant preclinical models that are moderately sensitive or resistant to MEK1/2 inhibition. This combination results in deeper and more durable suppression of the RAS/MAPK signaling pathway that is not achievable with single-agent treatment. The AZD0364 and selumetinib combination also results in significant tumor regressions in multiple KRAS-mutant xenograft models. The combination of ERK1/2 and MEK1/2 inhibition thereby represents a viable clinical approach to target KRAS-mutant tumors.

Inhibition of Mitogen-Activated Protein Kinase Kinase Alone and in Combination with Anaplastic Lymphoma Kinase (ALK) Inhibition Suppresses Tumor Growth in a Mouse Model of ALK-Positive Lung Cancer.

Anaplastic lymphoma kinase (ALK)-positive non-small-cell lung cancer most commonly arises through EML4 (Echinoderm Microtuble Like 4)-ALK chromosomal fusion. We have previously demonstrated that combination of the ALK inhibitor crizotinib with the MEK inhibitor selumetinib was highly effective at reducing cell viability of ALK-positive non-small-cell lung cancer (H3122) cells. In this study, we further investigated the efficacy of crizotinib and selumetinib combination therapy in an in vivo xenograft model of ALK-positive lung cancer. Crizotinib decreased tumor volume by 52% compared with control, and the drug combination reduced tumor growth compared with crizotinib. In addition, MEK inhibition alone reduced tumor growth by 59% compared with control. Crizotinib and selumetinib alone and in combination were nontoxic at the dose of 25 mg/kg, with values for ALT (<80 U/l) and creatinine (<2 mg/dl) within the normal range. Our results support the combined use of crizotinib with selumetinib in ALK-positive lung cancer but raise the possibility that a sufficient dose of an MEK inhibitor alone may be as effective as adding an MEK inhibitor to an ALK inhibitor. SIGNIFICANCE STATEMENT: This study contains in vivo evidence supporting the use of combination MEK inhibitors in ALK+ lung cancer research, both singularly and in combination with ALK inhibitors. Contrary to previously published reports, our results suggest that it is possible to gain much of the benefit from combination treatment with an MEK inhibitor alone, at a tolerable dose.

LBA73 - SELPAC: A 3 arm randomised phase II study of the MEK inhibitor selumetinib alone or in combination with paclitaxel (PT) in metastatic uveal melanoma (UM)

LBA73 - SELPAC: A 3 arm randomised phase II study of the MEK inhibitor selumetinib alone or in combination with paclitaxel (PT) in metastatic uveal melanoma (UM)

Abstract CT020: Phase I dose escalation of olaparib (PARP inhibitor) and selumetinib (MEK Inhibitor) combination in solid tumors with Ras pathway alterations

Abstract Background: Preclinical data from our team demonstrated that MEK inhibition increases antitumor efficacy of PARP inhibitors in tumors with Ras pathway alterations. We sought to identify dose limiting toxicities (DLTs) and maximum tolerated dose (MTD) of olaparib and selumetinib combination in solid tumors with Ras pathway alterations. Methods: Olaparib and selumetinib were given orally twice daily. Dose escalation with three planned dose levels (DL) was performed using the modified toxicity probability interval 2 design with toxicity assessed by CTCAE v4.03. RECIST criteria (v1.1) were used to assess response. Clinical benefit was defined as partial (PR) or complete response, or stable disease for 4 months or longer. Results: 14 patients are evaluable for toxicity in the dose escalation phase, and 12 patients are evaluable for response. Median age was 56.5 years, and 10/14 (71%) patients were female. Median number of prior treatments was 4 (1-9). Of the 14 patients enrolled, 11 had KRAS mutations, 1 amplified KRAS, 1 NRAS mutation and 1 amplified NRAS. The majority of patients had gynecologic cancers. 4 and 3 patients were treated at DL1 and DL2, respectively, and 7 patients at DL3. No DLTs were observed (Table 1). MTD was not reached. DL3 (olaparib 300mg; selumetinib 75mg) was confirmed as the recommended Phase II dose (RP2D). Of 12 evaluable patients, ORR was 17%, and CBR 33%. 2 patients had a PR: 1 patient with KRAS mutant primary peritoneal cancer, and 1 with NRAS mutant ovarian cancer. 2 patients remained on treatment for more than 15 months: 1 with KRAS mutant primary peritoneal cancer (on DL-1), and 1 with KRAS mutant non-small cell lung cancer (DL1). All patients with clinical benefit were BRCA wildtype. Conclusions: The combination of olaparib and selumetinib is well-tolerated at the identified RP2D. This combination also shows promising preliminary anti-tumor activity in patients with mutant RAS. Enrollment to expansion cohorts is ongoing. Table 1Grade 3/4 and Most Common Adverse Events. NOTE: No Grade 4 Events Occurred.Adverse EventGrade 3Any GradeAbdominal pain7%7%Acneiform Rash7%71%Anemia79%Anorexia29%Constipation29%Decreased ejection fraction7%14%Decreased white blood cell count7%36%Diarrhea50%Dizziness29%Dry mouth43%Dry skin29%Dysgeusia36%Edema29%Elevated aspartate aminotransferase7%50%Elevated bilirubin7%7%Elevated CPK7%36%Elevated creatinine29%Fatigue7%64%Hepatic pain7%7%Hypophosphatemia79%Nausea57%Neutropenia7%21%Oral mucositis50%Other skin effects36%Thromboembolic event7%7% Citation Format: Katherine C. Kurnit, Funda Meric-Bernstam, Kenneth Hess, Robert L. Coleman, Priya Bhosale, Katerina Savelieva, Filip Janku, David Hong, Aung Naing, Shubham Pant, Jordi Rodon, Timothy A. Yap, Anil K. Sood, Pamela T. Soliman, David M. Gershenson, Gordon B. Mills, Shannon N. Westin. Phase I dose escalation of olaparib (PARP inhibitor) and selumetinib (MEK Inhibitor) combination in solid tumors with Ras pathway alterations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT020.

Radiosensitization of HRAS-Mutant Bladder Cancer

The ability of activated HRAS to promote radiation resistance and predict for sensitivity to potential radiosensitizers was tested in a bladder cancer model system. Mutations in HRAS, KRAS, and NRAS were analyzed using cBioPortal in a bladder cancer cohort (TCGA). We employed a panel of urothelial carcinoma cell lines – T24 (HRASG12V), J82 and 5637 (RASWT). Cell growth and survival was tested with colony formation and proliferation assays. Radiation survival was assessed by clonogenic survival assay. Immunoblots were used to confirm mutant HRAS expression, and target activation/knockdown in overexpression and knockdown studies. Radiosensitization of mutant-HRAS bladder cancer was tested using a flank cell line xenograft model in nude mice. Approximately 10% of bladder cancers feature alterations in one of three RAS genes; mutations in HRAS comprise greater than 50% of these. An HRAS activating (G12V) mutation was detected in T24. Consistent with other cancer lines featuring activated RAS, T24 is relatively insensitive to radiation. Direct inhibition of the MEK/ERK or PI3K/MTOR pathway by selumetinib or BEZ-235, respectively, decreased target protein activation and resulted in significant growth inhibition compared to control (p<0.05). Treatment with either selumetinib or BEZ-235 radiosensitized HRASG12V expressing cells (SER 1.3-1.8), but had more modest effects on cells with wildtype HRAS. Compared to control, T24 exhibited higher levels of phosphorylated DNA-PK and γH2AX one hour after combination treatment with radiation and selumetinib or BEZ-235. siRNA knockdown of HRAS radiosensitized T24, but not J82 or 5637 cells relative to non-targeting control. The combination of selumetinib and radiation therapy significantly delayed the growth of T24 tumors in vivo. Over 10% of bladder cancers feature alterations in the RAS family of genes. These mutations often lead to resistance to conventional therapies, including radiation. Inhibition of downstream MEK/ERK and PI3K/MTOR pathways can radiosensitize tumors with activating mutations in HRAS. Identification of additional mutation/drug combinations that result in radiosensitization may be valuable to advance the design of personalized radiation therapy.

Abstract 5782: Selumetinib-based therapy in uveal melanoma patient-derived xenografts

Abstract Purpose: The prognosis of metastatic uveal melanoma (UM) patients remains one of the worst observed in human cancers. The identification of frequently mutated GNAQ/GNA11 and the activation of MAPK signaling in UM raise the possibility of using efficient targeted therapies such as MEK inhibition. The aim of our study was to evaluate drug combinations that might enhance the efficacy of the MEK inhibitor, selumetinib (AZD6244, ARRY-142886), using patient-derived xenografts. Materials: Five UM PDXs were used in this study, i.e., MP34, MP46, MP55, MP77, and MM26, all mutated for GNAQ or GNA11. Selumetinib was administered alone or combined with chemotherapies (dacarbazine and docetaxel) or targeted therapies: the ERK inhibitor, AZ6197 and the mTORC1/2 inhibitor, vistusertib (AZD2014). All targeted therapies were administered orally five days/week at the following doses: selumetinib at 25 mg/kg/day BID, AZ6197 at 50 mg/kg QD, AZD2014 at 15mg/kg QD. Dacarbazine was administered at 40 mg/kg for 5 consecutive days every 28 days and docetaxel at 15 mg/kg weekly. Both were administered intraperitoneally. Results: The combination of selumetinib and dacarbazine did not show improvement of antitumor efficacy in MP34, MM26 and MP55.The results showed a slight increase of overall response rate when selumetinib was combined with docetaxel, in comparison to the treatment with selumetinib or docetaxel alone. Importantly, we observed a significant antitumor effect when selumetinib was used in combination with AZ6197 or AZD2014 with respect to the monotherapies. Preliminary pharmacodynamics studies showed variation of the expression of p-ERK and also p-AKT and/or p-S6 when UM PDX were treated with AZ6197 or AZD2014 alone or in combination with selumetinib. Conclusion: Our data suggest that ERK and mTORC1/2 targeting could represent promising therapeutic approaches for the treatment of metastatic UM patients. Citation Format: Didier Decaudin, Rania EL Botty, Béré Diallo, Gerald Massonnet, Justine Fleury, Adnan Naguez, Marine Dubois, Emma J. Davies, Aaron Smith, Joanne Wilson, Colin Howes, Paul Smith, Nathalie Cassoux, Pascale Mariani, Sophie Piperno-Neumann, Sergio Roman Roman, Fariba Nemati. Selumetinib-based therapy in uveal melanoma patient-derived xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5782.

Abstract 856: Selection of radiosensitizers based on HRAS mutation in bladder cancer

Abstract Purpose/Objective(s): The ability of activated HRAS to promote radiation resistance and predict for sensitivity to potential radiosensitizers was tested in a bladder cancer model system. Materials/Methods: Mutations in HRAS, KRAS, and NRAS were analyzed using cBioPortal in a bladder cancer cohort (TCGA). We employed a panel of urothelial carcinoma cell lines-T24 (HRASG12V), J82 and 5637 (RASWT). Cell growth and survival was tested with colony formation and proliferation assays. Radiation survival was assessed by clonogenic survival assay. Immunoblots were used to confirm mutant HRAS expression, and target activation/knockdown in overexpression and knockdown studies. Radiosensitization of mutant-HRAS bladder cancer was tested using a flank cell line xenograft model in nude mice. Results: Approximately 10% of bladder cancers feature alterations in one of three RAS genes; mutations in HRAS comprise greater than 50% of these. An HRAS activating (G12V) mutation was detected in T24. Consistent with known roles for activated RAS, T24 is relatively insensitive to both cetuximab and radiation. Using both in vivo and in vitro studies, cetuximab exhibited no radiosensitization of T24. Treatment with cetuximab lowered AKT, but not ERK activation. Direct inhibition of the MEK/ERK or PI3K/MTOR pathway by selumetinib or BEZ235, respectively, decreased target protein activation and resulted in significant growth inhibition compared to control (p&amp;lt;0.05). Treatment with either selumetinib or BEZ235 radiosensitized HRASG12V expressing cells (SER 1.3-1.8), but had more modest effects on cells with wild-type HRAS. siRNA knockdown of HRAS radiosensitized T24, but not J82 or 5637 cells relative to non-targeting control. The combination of selumetinib and radiation therapy delayed the growth of T24 tumors in vivo. Conclusions: Over 10% of bladder cancers feature alterations in the RAS family of genes. These mutations can lead to resistance to cetuximab, either as a single treatment or as a radiosensitizer. Inhibition of downstream MEK/ERK and PI3K/MTOR pathways can radiosensitize tumors with activating mutations in HRAS. Identification of additional mutation/drug combinations that result in radiosensitization may be valuable to advance the design of personalized radiation therapy. Citation Format: Michael M. Fisher, Adam D. Swick, Kwangok P. Nickel, Randall J. Kimple. Selection of radiosensitizers based on HRAS mutation in bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 856.

Abstract 1856: Combination of the novel ERK inhibitor AZD0364 with the MEK inhibitor selumetinib significantly enhances antitumor activity in KRAS mutant tumor models

Abstract The RAS/MAPK pathway is a major driver in oncogenesis and is dysregulated in approximately 30% of human cancers, primarily by mutations in BRAF or RAS genes. While BRAF and MEK inhibitors improve BRAF mutant melanoma patient outcomes, single-agent pathway inhibitors have demonstrated limited clinical benefit. Therefore, combined inhibition of multiple nodes within the RAS/MAPK pathway may be necessary to effectively suppress pathway signaling and achieve meaningful clinical benefit, specifically in patients with KRAS mutant tumors. AZD0364 is a potent and highly selective inhibitor of ERK1 and ERK2. AZD0364 exhibits high cellular potency against a direct substrate (e.g., inhibition of phosphorylation of p90RSK in BRAF mutant A375 cells, IC50 = 6 nM) and is highly (10/329 kinases tested are inhibited at &amp;gt;50% at 1 µM). In an unbiased cell proliferation screen of 750 tumor cell lines, &amp;gt;50% of cell lines that are sensitive to AZD0364 have RAS/MAPK pathway genetic alterations such as BRAF, NRAS or KRAS mutations. In a subset of KRAS mutant NSCLC cell lines, combined treatment of AZD0364 and selumetinib (AZD6244, ARRY-142886) is highly synergistic. This combination results in deeper and more durable suppression of the RAS/MAPK pathway that is not achievable with single-agent treatment, as assessed by phospho-p90RSK, change in transcriptional signatures and induction of apoptotic biomarkers. The AZD0364 and selumetinib combination also significantly suppresses RAS/MAPK pathway output and tumor growth in vivo to a greater extent than achievable with either agent given as a monotherapy. This combination is well tolerated in vivo and delivers 65% tumor regression in the NCI H358 KRAS mutant NSCLC xenograft model. This combination also results in significant tumor regressions in both A549 and HCT116 KRAS mutant xenografts. These data demonstrate that combined AZD0364 and selumetinib is well tolerated, effectively suppresses RAS/MAPK pathway signalling and delivers durable regressions in preclinical models. The combination of ERK and MEK inhibition represents a viable clinical approach to target KRAS mutant tumors. Citation Format: Vikki Flemington, Iain Simpson, Jason Breed, Emma Davies, Francis Gibbons, Phillip Hopcroft, Nicola Lyndsay, Christopher Jones, Clifford Jones, David Robinson, Claire Rooney, Karen Roberts, Linda Sandin, Richard Ward, Pei Zhang, Elizabeth Pease. Combination of the novel ERK inhibitor AZD0364 with the MEK inhibitor selumetinib significantly enhances antitumor activity in KRAS mutant tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1856.

Pan-RAF and MEK vertical inhibition enhances therapeutic response in non-V600 BRAF mutant cells

BackgroundCurrently, there are no available targeted therapy options for non-V600 BRAF mutated tumors. The aim of this study was to investigate the effects of RAF and MEK concurrent inhibition on tumor growth, migration, signaling and apoptosis induction in preclinical models of non-V600 BRAF mutant tumor cell lines.MethodsSix BRAF mutated human tumor cell lines CRL5885 (G466 V), WM3629 (D594G), WM3670 (G469E), MDAMB231 (G464 V), CRL5922 (L597 V) and A375 (V600E as control) were investigated. Pan-RAF inhibitor (sorafenib or AZ628) and MEK inhibitor (selumetinib) or their combination were used in in vitro viability, video microscopy, immunoblot, cell cycle and TUNEL assays. The in vivo effects of the drugs were assessed in an orthotopic NSG mouse breast cancer model.ResultsAll cell lines showed a significant growth inhibition with synergism in the sorafenib/AZ628 and selumetinib combination. Combination treatment resulted in higher Erk1/2 inhibition and in increased induction of apoptosis when compared to single agent treatments. However, single selumetinib treatment could cause adverse therapeutic effects, like increased cell migration in certain cells, selumetinib and sorafenib combination treatment lowered migratory capacity in all the cell lines. Importantly, combination resulted in significantly increased tumor growth inhibition in orthotropic xenografts of MDAMB231 cells when compared to sorafenib - but not to selumetinib – treatment.ConclusionsOur data suggests that combined blocking of RAF and MEK may achieve increased therapeutic response in non-V600 BRAF mutant tumors.

Selumetinib-based therapy in uveal melanoma patient-derived xenografts.

The prognosis of metastatic uveal melanoma (UM) is among the worst of all human cancers. The identification of near-ubiquitous GNAQ/GNA11 mutations and the activation of MAPK signaling in UM have raised hopes of more effective, targeted therapies, based on MEK inhibition, for example. We evaluated the potential of drug combinations to increase the efficacy of the MEK inhibitor selumetinib (AZD6244, ARRY-142886), in UM cell lines and Patient-Derived Xenografts. We first evaluated the combination of selumetinib and DTIC. We found that DTIC did not improve the in vitro or in vivo antitumor efficacy of selumetinib, consistent with the outcome of the SUMIT clinical trial assessing the efficacy of this combination in UM. We then tested additional selumetinib combinations with the chemotherapy agent docetaxel, the ERK inhibitor AZ6197, and the mTORC1/2 inhibitor, vistusertib (AZD2014). Combinations of selumetinib with ERK and mTORC1/2 inhibitors appeared to be the most effective in UM PDX models.

Palbociclib, a selective CDK4/6 inhibitor, enhances the effect of selumetinib in RAS-driven non-small cell lung cancer

KRAS is one of the most commonly mutated oncogenes in non-small cell lung cancer (NSCLC). Resistance to MEK inhibitor monotherapy develops through a variety of mechanisms. CDK4 was reported to have a synthetic lethal interaction with KRAS. In this study, we demonstrated the combination effects of the MEK inhibitor selumetinib and the CDK4/6 inhibitor palbociclib in RAS-driven NSCLC. In vitro, cell lines with CDKN2A mutations were insensitive to selumetinib. We used siRNA and pharmacologic inhibition of CDK4 and found that the combination of selumetinib and palbociclib synergistically inhibited RAS-driven NSCLC cases with CDKN2A mutations but not those with wild type CDKN2A. The combination treatment potentiated growth inhibition and increased the population of cells in G1 phase. Selumetinib completely inhibited p-ERK but not p-RB. The addition of palbociclib markedly inhibited p-RB and downregulated survivin expression. In vivo, the combination treatment inhibited the growth of NSCLC xenografts, which correlated with decreased levels of p-RB, downregulated survivin and decreased Ki-67 staining. These data suggest that the combination treatment of palbociclib and selumetinib is effective in preclinical models of RAS-driven NSCLC with CDKN2A mutations.