BRAF MEK Inhibitors Research Articles

Recent advances in therapeutic strategies of Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare form of non-LCH characterized by excessive accumulation of histiocytes in various tissues, leading to significant morbidity. The estimated prevalence of ECD is low, with fewer than 1000 cases reported globally, yet it presents considerable clinical challenges due to its heterogeneous manifestations, which include bone pain, cardiovascular complications, and neurological symptoms. Traditional treatment approaches, primarily involving corticosteroids and chemotherapy, have limitations, including inconsistent responses and significant side effects. Recent advances in understanding the pathogenesis of ECD, particularly the role of the BRAF V600E mutation, have led to the exploration of novel therapeutic strategies, such as targeted BRAF inhibitors, MEK and mTOR inhibitors, and other immunotherapies, which offer promise in improving patient outcomes. The review further explores clinical manifestations, and radiographic features of Erdheim-Chester disease, and discusses treatment strategies, current clinical studies in the field of ECD. By integrating these aspects, this review aims to provide a thorough understanding of ECD and its evolving treatment landscape, ultimately contributing to improved patient outcomes.

Survival improvements in patients with melanoma brain metastases and leptomeningeal disease in the modern era: Insights from a nationwide study (2015-2022).

Advances in modern therapies have improved outcomes for patients with melanoma brain metastases (MBM), though prognosis remains poor. The optimal treatment strategy for patients who do not meet clinical trial inclusion criteria is unclear. This study included all patients with MBM diagnosed in Denmark between 2015 and 2022, identified through the Danish Metastatic Melanoma Database (DAMMED) and local surgical and radiotherapy records. Data were collected from electronic patient records. A total of 838 patients were included, with a median overall survival (OS) of 9.0 months. Of these, 112 (19.4 %) survived beyond 3 years post-diagnosis. Patients treated with immune checkpoint inhibitors (ICI) as first line treatment, specifically ipilimumab + nivolumab, demonstrated an intracranial overall response rate (icORR) of 46 % and a 2-year OS of 49 %. Those treated with BRAF/MEK inhibitors (BRAF/MEKi) had an icORR of 56 % but a 2-year OS of 20 %. Patients with leptomeningeal disease (LMD, n = 67) had a median OS of 8.4 months. Systemic therapy was associated with a superior OS for patients with LMD, though no survival benefit was seen with ICI compared to BRAF/MEKi. Among the 230 patients who underwent surgery, 30 received postoperative stereotactic radiosurgery (SRS); however, there was no difference in OS or intracranial progression-free survival between the groups. A considerable proportion of patients with brain metastases diagnosed after 2015 survived more than 3 years. Patients with LMD appeared to obtain limited benefit of ICI with only few patients alive > 3 years post-diagnosis.

Regorafenib Combined with BRAF/MEK Inhibitors for the Treatment of Refractory Melanoma Brain Metastases.

There are no active treatment options for patients with progressive melanoma brain metastases (MBM) failing immune checkpoint blockade (ICB) and BRAF/MEK inhibitors (BRAF/MEKi). Regorafenib (REGO), an oral multi-kinase inhibitor (incl. RAF-dimer inhibition), can overcome adaptive resistance to BRAF/MEKi in preclinical models. This is a single-center retrospective case series of patients with refractory MBM treated with REGO plus BRAF/MEKi (compassionate use). A total of 22 patients were identified (18 BRAF-mutant, 4 NRASQ61-mutant; 19 with progressive MBM; 11 on corticosteroids). Thirteen BRAFV600-mutant patients were progressing on BRAF/MEKi at the time of REGO association. BRAF-mutant patients received REGO (40-80 mg once daily) combined with BRAF/MEKi, NRAS-mutant patients were treated with REGO + MEKi (+low-dose BRAFi to mitigate skin-toxicity). Grade 3 TRAE included arterial hypertension (n = 4) and maculopapular rash (n = 3). There were no G4/5 TRAE. In BRAF-mutant patients, overall and intracranial objective response rates (overall ORR and IC-ORR) were 11 and 29%, and overall and intracranial disease control rates (overall DCR and IC-DCR) were 44 and 59%, respectively. In NRAS-mutant patients overall ORR and IC-ORR were 0 and 25% and overall DCR and IC-DCR were 25 and 50%, respectively. The median PFS and OS were, respectively, 7.1 and 16.4 weeks in BRAF-mutant and 8.6 and 10.1 weeks in NRAS-mutant patients. In heavily pretreated patients with refractory MBM, REGO combined with BRAF/MEKi demonstrated promising anti-tumor activity with an acceptable safety profile. In BRAFV600-mutant melanoma patients, responses cannot solely be attributed to BRAF/MEKi rechallenge. Further investigation in a prospective trial is ongoing to increase understanding of the efficacy.

Abstract C038: Harnessing NK cells to improve targeted therapy therapeutic efficacy in BRAF- mutant melanoma

Abstract Malignant melanoma is the most lethal form of skin cancer, with BRAFV600E as the most common driver mutation. Despite the success of BRAF/MEK inhibitors (BRAF/MEKi) as a standard-of-care, drug resistance occurs at high frequency and remains a concern to be overcome. In addition to suppressing cancer cell proliferation and survival, BRAF/MEKi treatment alters the tumor microenvironment to favor anti-tumor immunity, with extensive previous studies focusing on the T cell compartment. Investigating other immune components, such as natural killer (NK) cells, may offer new insights into improving the overall effectiveness of BRAF/MEKi. NK cells are innate immune cells that provide activating signals to cytotoxic T cells, in addition to their critical roles in tumor surveillance and metastasis. However, the role of NK cells as a component of the BRAF/MEKi response in melanoma remains largely unknown. To investigate the role of NK cells in BRAF/MEKi-mediated tumor control, we depleted NK cells in melanoma-bearing mice. We found that the tumors developed full resistance faster in the NK cell-depleted group than in controls. Moreover, quantification of tumor-infiltrating NK cells in different melanoma phases, including off-therapy growth, therapy-induced regression, drug- tolerant residual disease, and on-therapy regrowth and resistance, revealed a positive correlation between NK cell infiltration and the tumor response to BRAF/MEKi. We further increased NK cell infiltration during drug-tolerant residual disease by inhibiting Ptpn22, a potential negative regulator of activity in NK and other immune cell populations, resulting in a delayed onset of therapy resistance. These results demonstrate the indispensable role of NK cells in the BRAF/MEKi tumor response and their potential to improve the therapeutic efficacy of BRAF/MEKi. Citation Format: Chia-Hsin Hsu, Andrew C. White. Harnessing NK cells to improve targeted therapy therapeutic efficacy in BRAF- mutant melanoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C038.

Abstract A023: Arachidonic acid metabolism promoting cross resistance in melanoma cells

Abstract Melanoma patients initially respond well to first line immunotherapy. However, cross resistance to immunotherapy and BRAF/MEK inhibitor is a clinical challenge for melanoma care. To investigate drug tolerant and resistant mechanisms promoting cross resistance, we analyzed RNA-sequencing and gene set enrichment targeted therapy resistant melanoma cells revealing an enriched arachidonic acid gene signature. Intracellular arachidonic acid levels were increased in drug resistant and drug tolerant melanoma models. Arachidonic acid is enzymatically converted by COX1 and COX2 to prostaglandins, which is subsequently secreted into the microenvironment. Drug tolerant and resistant cells had increased protein expression of COX1 and COX2 concurrently with increased secretion of prostaglandin E2. COX1/2 inhibition and COX2 knockdown in vitro had no effect on cell growth in drug tolerant or resistant cells compared to parental cells. However, secreted prostaglandins are known immunomodulators, thus we explored how COX1/2 inhibition in combination with BRAF inhibitor plus MEK inhibitor affected immune cell infiltration. COX1/2 inhibition increased CD4+ and CD8+ T cell infiltration as compared to BRAF inhibitor plus MEK inhibitor alone. Under constant BRAF inhibitor plus MEK inhibitor treatment, we found that COX1/2 inhibition upon reaching MRD status prevented tumor relapse in vivo and increased survival dependent on an immune system. Future studies will evaluate the importance of arachidonic acid metabolism in promoting cross resistance to immune checkpoint blockade and whether T cell depletion prevents the delayed tumor relapse. Overall, COX1/2 inhibition delayed tumor relapse and survival in an immune-dependent manner and demonstrated a potential cross resistant mechanism. Citation Format: Casey D. Stefanski, Daniel A. Erkes, Timothy J. Purwin, Glenn L. Mersky, Erica L. Kitterman, Manal Mustafa, Jelan Haj, Diana Melissaratos, Andrew E. Aplin. Arachidonic acid metabolism promoting cross resistance in melanoma cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A023.

TMOD-03.BRAFV600E MUTATION INDUCES TWIST1 UPREGULATION ASSOCIATED WITH MIGRATION AND CEREBRAL FLUID DISSEMINATION IN GLIOBLASTOMA

Abstract INTRODUCTION BRAFV600E-mutant glioblastoma (GBM) with epithelioid features frequently show cerebrospinal fluid dissemination (CSFD), which results in poor prognoses. BRAF mutation is worth investigating since BRAF or downstream MEK inhibitors show dramatic response for BRAFV600E-mutant GBM including CSFD. This suggests BRAF mutation could play a role for inducing the clinical manifestation of CSFD found in newly diagnosed and recurrent BRAFV600E-mutant GBM. Because, BRAFV600E-mutant GBM often recur with CSFD, elucidating the mechanism by which BRAFV600E-mutant GBM exhibits CSFD is important to improve prognosis. (Objective) To elucidate the molecular mechanism of CSFD involved in BRAFV600E-mutant GBM. METHODS We introduced the heterozygous BRAFV600E mutation in human induced pluripotent stem cells (iPSC) in the context of GBM genetic alterations, CDKN2A/2B, and PTEN deletion, TERT promoter mutation and with EGFRvIII overexpression. We implanted these iPSC-derived neural progenitor cells into immunodeficient mouse brains to establish a BRAFV600E-mutant GBM model. At the same time, we created a model with the same genetic background without BRAFV600E. We compared their gene expression, pathology, and migration patterns to identify BRAFV600E specific characteristics. RESULTS RNA sequencing revealed BRAFV600E-mutant tumors upregulated migration, and downregulated cell-to-cell adhesion genes. TWIST1 was one of the most upregulated genes, and was validated by qPCR. Concomitant with TWIST1 expression we detected downregulation of E-cadherin. The BRAFV600E GBM model histologically showed a cluster-like invasion phenotype, while non-BRAF tumors showed homogenous invasion with typical GBM pathological findings. Immunohistochemical staining showed relatively high TWIST1 expression in cluster-like tumor cells of BRAFV600E tumors. Upon re-engraftment of primary tumor-derived cells, secondary BRAFV600E tumors presented leptomeningeal dissemination. TWIST1 knockdown resulted in a decrease in the migratory ability of our BRAFV600E model in vitro, and is under investigation in vivo. CONCLUSION BRAV600E mutation induces TWIST1 upregulation, and might facilitate migration and CSFD. This work nominates TWIST1 and its regulated genes as targets for BRAFV600E-mutant GBM with CSFD.

CSIG-29. BRAF INHIBITOR THERAPY IN BRAF-MUTATED PRIMARY BRAIN TUMORS: A SINGLE-CENTER EXPERIENCE

Abstract BACKGROUND BRAF pathway alterations are frequent in glial/neuroepithelial tumors. BRAF-targeted therapy with BRAF inhibitors (BRAFi) and/or MEK inhibitors (MEKi) has proven efficacy in clinical trials, though mainly enrolling pediatric patients. We sought to investigate real-world data for adult patients with BRAF-pathway mutant glial/neuroepithelial neoplasms treated with BRAFi/MEKi. METHODS Adults with BRAF-pathway mutated glial/neuroepithelial neoplasms treated with BRAFi/MEKi were retrospectively reviewed. RESULTS Five patients (n=4 female, median age at diagnosis 36) were identified (tumor types: glioblastoma n=1, high-grade astrocytoma with epithelioid features n=1, low-grade neuroepithelial tumor n=1, pilocytic astrocytoma n=1, pleomorphic xanthoastrocytoma n=1). Four had BRAF V600E and one had NF1 p.S2687Cfs*5 mutant tumors. Prior to targeted therapy initiation, patients underwent a median 2.4 treatments including surgery (n=4), radiation therapy (n=4), chemotherapy (temozolomide n=4; carboplatin/vincristine n=1). BRAF-targeted therapies included dabrafenib/trametinib (n=4), binimetinib/encorafenib (n=2), binimetinib (n=2). One NF1-mutant glioblastoma received binimetinib followed by binimetinib/bevacizumab. Median BRAFi/MEKi treatment was 15.2 months (range: 6-36 months). Toxicities included leukopenia (n=3), peripheral edema (n=1), reduced ejection fraction (n=1), skin rash (n=5), transaminitis (n=1) with all patients requiring dose reductions and 3 cases requiring discontinuation. Among patients where BRAFi/MEKi was discontinued due to toxicity, 2 received other treatments at progression, then switched to a different BRAFi/MEKi combination, which they tolerated (duration 6-10months). Best radiographic response was partial response, noted in 3 patients treated with dabrafenib/trametinib. Four patients remain alive and continue BRAFi/MEKi. CONCLUSIONS In this cohort of heavily-pretreated patients with glial/neuroepithelial neoplasms, BRAF-targeted therapy was associated with durable responses. Interestingly, two patients who were unable to tolerate one combination of BRAFi/MEKi were able to tolerate a different combination with sustained response. Our findings support ongoing use of BRAF targeted therapy for CNS tumors. Optimal timing and duration of treatment requires further prospective evaluation in adult patients.

New emerging treatment options for metastatic melanoma: a systematic review and meta-analysis of skin cancer therapies.

Skin cancer, notably melanoma, poses a significant global health burden, with rising incidence and mortality rates. While therapeutic advancements have improved outcomes, metastatic melanoma remains challenging to treat. This study aims to systematically review systemic treatment options for advanced melanoma, focusing on efficacy and safety in the first-line setting. Through a comprehensive search and meta-analysis of randomized controlled trials conducted from 2013 to 2023, 11 studies encompassing 2816 participants were analyzed. Treatment options included BRAF inhibitors (vemurafenib, dabrafenib), MEK inhibitors (trametinib, cobimetinib), and immune checkpoint inhibitors (ipilimumab). Combined therapy with vemurafenib, cobimetinib, and ipilimumab demonstrated superior overall survival (OS) and progression-free survival (PFS) compared to monotherapy, with a significant odds ratio (OR) of 6.95 (95% CI: 4.25-9.64, p < 0.00001) for OS and 2.49 (95% CI: 1.42-3.56, p < 0.00001) for PFS. Additionally, dabrafenib and trametinib combination therapy showed improved outcomes with favorable tolerability, including a significant reduction in adverse event (AE) risk, with an OR of 2.20 (95% CI: 1.72-2.81). Furthermore, our analysis highlighted vemurafenib-associated dermatological toxicities, emphasizing the need for effective management strategies. The study underscores the evolving treatment landscape in melanoma management, with a potential shift towards immune checkpoint inhibitors in the adjuvant setting, particularly for BRAF-mutated disease. However, limitations in meta-analysis methodologies and the need for long-term investigations into treatment implications on survival and quality of life underscore the importance of continued research.

Update on the treatment of BRAFmut metastatic melanoma and future perspectives

Abstractv‐Raf murine sarcoma viral oncogene homolog B (BRAF) mutations were first identified in melanoma in 2002, leading to increased cell division and proliferation, and resultant tumour growth. The identification and characterisation of BRAF mutations (BRAFmut) led to the development of several highly specific, BRAF‐, then mitogen‐activated kinase enzyme (MEK)‐targeted therapies that have enabled rapid tumour responses and improved treatment outcomes in most patients with metastatic BRAFmut melanoma. The combination of these two drug classes (BRAF inhibitors and MEK inhibitors) has demonstrated improved response rates, progression‐free survival, and overall survival (OS), along with a more tolerable safety profile, compared with BRAF inhibition alone. In parallel, improved knowledge of the immune system has enabled the development of immune checkpoint inhibitors (ICIs), although immune‐related adverse events with ICIs may prove to be problematic in some patients and require careful management. While targeted therapy appears to provide rapid disease control in a relatively high proportion of patients, the development of secondary resistance may limit the overall duration of responses. Acquired resistance, along with primary resistance, has also been reported for ICIs, with a lower overall response rate to that with targeted therapy, although durable responses have been reported in some responding patients. A combination strategy of targeted therapy with ICIs has demonstrated modest increases in efficacy compared with targeted therapy combinations, although data significance varies across studies, there is increased risk of toxicity, and triple combination therapy has not yet received clinical approval in Europe. Thus, there is an ongoing need to establish optimal sequencing of these treatments in patients with advanced BRAFmut melanoma, and this has become the focus of current research. The aim of this narrative review was to provide an update on the treatment of BRAFmut metastatic melanoma, current guideline recommendations, and future clinical perspectives.

Triple combination of vemurafenib, cobimetinib, and atezolizumab in real clinical practice in the Russian Federation: results of the A1 cohort of the ISABELLA study.

Among several treatment options for BRAF-mutant metastatic melanoma, a combination of BRAF inhibitor, MEK inhibitor, and anti-PDL1 antibody seems to be a new emergent approach recently registered in the Russian Federation. It is still not clear which patient population benefits more from this simultaneous use of three drugs instead of its sequencing. This study aimed to evaluate patients' characteristics treated in real practice in 14 Russian regions by triple combination and to analyze their outcomes depending on biomarkers (PD-L1 expression). This was a part (cohort A1) of a prospective non-interventional study of clinical outcomes and biomarkers in patients with skin melanoma. Patients were included in cohort A1 if combination treatment with vemurafenib (vem) + cobimetinib (cobi) + atezolizumab (atezo) was initiated no earlier than 12 weeks (84 days) prior to written informed consent to participate in this study. The index event was the initiation of therapy with all three drugs vem + cobi + atezo (i.e., triple combination). The primary efficacy endpoint of the study was the 24-month overall survival (OS), defined as the time from the index date to the date of death from any cause. If the patient did not experience an event, the OS will be censored at the date of the last contact. Objective response rate (ORR), duration of response (DoR), and progression-free survival (PFS) in the Intention to treat (ITT) population, in biomarker positive population, and in population with brain metastases were also evaluated. Quality of life questionnaires were pre-planned by protocol if it was a part of routine practice. Adverse events were also collected. Between March 2021 and May 2023, 59 patients were enrolled in 19 centers from 14 regions of Russia. Thirty-one of 59 (52.4%) patients had central nervous system metastases, and 18 of 31 (58.4%) were symptomatic. Forty of 59 patients (68%) received the triple combination as the first-line treatment. The median follow-up period was 16.83 [95% confidence interval (CI) 13.8-19.8] months. The mean duration of therapy with this regimen was 9.95 months (95% CI 7.48-13.8). ORR was 55.1%; progression as the best outcome was seen in 16.3%. The median DoR was 12.95 months (95% CI 11.0-14.8 months), with a median of 20.3 months (95% CI 9.1-31.5 months) when triple therapy was administered in the first-line treatment. In patients with brain metastases (N = 31), ORR was 45.1%; the median DoR was 12.95 (95% CI 11.0-14.8 months). The median PFS in the entire population was 13.6 months (95% CI 8.6-18.6); the 24-month PFS was 22%. The estimated median OS in the entire population was 15.8 months (95% CI NA); 24-month OS was 45% (95% CI 0.32-0.64). In multivariate Cox regression model, biomarkers of interest [lactate dehydrogenase, Programmed cell death ligand-1 (PD-L1)] did not have statistically significant impact on PFS, OS, or DoR probably due to high data missing rate. No unexpected adverse events were reported. Grades 3-4 AEs were seen in 23 of 59 patients (38%) with most common were skin and liver toxicity. Triple combination of atezolizumab, vemurafenib, and cobimetinib had proven its efficacy and tolerability in real settings. No impact of potential predictive biomarkers was seen (NCT05402059).

Current State of Targeted Therapy in Adult Langerhans Cell Histiocytosis and Erdheim-Chester Disease.

The mitogen-activated protein kinase (MAPK) pathway is a key driver in many histiocytic disorders, including Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD). This has led to successful and promising treatment with targeted therapies, including BRAF inhibitors and MEK inhibitors. Additional novel inhibitors have also demonstrated encouraging results. Nevertheless, there are several problems concerning targeted therapy that need to be addressed. These include, among others, incomplete responsiveness and the emergence of resistance to BRAF inhibition as observed in other BRAF-mutant malignancies. Drug resistance and relapse after treatment interruption remain problems with current targeted therapies. Targeted therapy does not seem to eradicate the mutated clone, leading to inevitable relapes, which is a huge challenge for the future. More fundamental research and clinical trials are needed to address these issues and to develop improved targeted therapies that can overcome resistance and achieve long-lasting remissions.

Tretinoin synergistically enhances the antitumor effect of combined BRAF, MEK, and EGFR inhibition in BRAFV600E colorectal cancer.

Patients with BRAF-mutated colorectal cancer (BRAFV600E CRC) are currently treated with a combination of BRAF inhibitor and anti-EGFR antibody with or without MEK inhibitor. A fundamental problem in treating patients with BRAFV600E CRC is intrinsic and/or acquired resistance to this combination therapy. By screening 78 compounds, we identified tretinoin, a retinoid, as a compound that synergistically enhances the antiproliferative effect of a combination of BRAF inhibition and MEK inhibition with or without EGFR inhibition on BRAFV600E CRC cells. This synergistic effect was also exerted by other retinoids. Tretinoin, added to BRAF inhibitor and MEK inhibitor, upregulated PARP, BAK, and p-H2AX. When either RARα or RXRα was silenced, the increase in cleaved PARP expression by the addition of TRE to ENC/BIN or ENC/BIN/CET was canceled. Our results suggest that the mechanism of the synergistic antiproliferative effect involves modulation of the Bcl-2 family and the DNA damage response that affects apoptotic pathways, and this synergistic effect is induced by RARα- or RXRα-mediated apoptosis. Tretinoin also enhanced the antitumor effect of a combination of the BRAF inhibitor and anti-EGFR antibody with or without MEK inhibitor in a BRAFV600E CRC xenograft mouse model. Our data provide a rationale for developing retinoids as a new combination agent to overcome resistance to the combination therapy for patients with BRAFV600E CRC.

Canadian Consensus for Treatment of BRAF V600E Mutated Pediatric and AYA Gliomas.

Background: The treatment of BRAF V600E gliomas with BRAF inhibitors (BRAFis) and MEK inhibitors (MEKis) has been increasingly integrated into clinical practice for pediatric low-grade gliomas (PLGGs) and pediatric high-grade gliomas (HGGs). However, some questions remain unanswered, such as the best time to start targeted therapy, duration of treatment, and discontinuation of therapy. Given that no clinical trial has been able to address these critical questions, we developed a Canadian Consensus statement for the treatment of BRAF V600E mutated pediatric as well as adolescent and young adult (AYA) gliomas. Methods: Canadian neuro-oncologists were invited to participate in the development of this consensus. The consensus was discussed during monthly web-based national meetings, and the algorithms were revised until a consensus was achieved. Results: A total of 26 participants were involved in the development of the algorithms. Two treatment algorithms are proposed, one for the initiation of treatment and one for the discontinuation of treatment. We suggest that most patients with BRAF V600E gliomas should be treated with BRAFis ± MEKis upfront. Discontinuation of treatment can be considered in certain circumstances, and we suggest a slow wean. Conclusions: Based on expert consensus in Canada, we developed algorithms for treatment initiation of children and AYA with BRAF V600E gliomas as well as a discontinuation algorithm.

Adjuvant BRAF/MEK versus anti-PD-1 in BRAF-mutant melanoma: Propensity score–matched recurrence-free, distant metastasis-free, and overall survival analysis.

9573 Background: Adjuvant BRAF/MEK inhibitors (BRAF/MEKi) and immunotherapy with anti-PD-1 have become the standard of care for resected high-risk stage III and IV melanoma, but a head-to-head comparison is lacking. In our earlier study, we compared adjuvant BRAF/MEKi and anti-PD-1 in a nationwide cohort in the Netherlands. However, the follow-up was too limited for overall survival (OS) analysis. We present an updated analysis including OS with extended follow-up. Methods: We included all resected high-risk stage III melanoma patients treated with first-line adjuvant BRAF/MEKi and anti-PD-1 from the Dutch Melanoma Treatment Registry from 2018-2023. We performed a propensity score matched outcome analysis of 1- and 2-year recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and OS. Grade ≥ 3 toxicity rates and discontinuation rates due to toxicity were described. Results: In total, 225 BRAF/MEKi-treated patients and 729 anti-PD-1-treated patients were included. BRAF/MEKi-treated patients had lower disease stages (16.4% versus 10.2% stage IIIA disease; p=0.01) and more comorbidities (76.0% versus 63.8%; p&lt;0.01) than anti-PD-1-treated patients. Median follow-up duration was 20.9 months. Two similar groups of 213 patients each were created by propensity score matching. Before matching, RFS and DMFS were significantly shorter in the anti-PD-1 treated patients, OS was not (Table). After matching, the 1- and 2-year RFS, DMFS and OS rates were not significantly different (Table). Toxicity data will be presented at the meeting. Conclusions: Our results suggest no significant differences in outcomes between adjuvant BRAF/MEKi and anti-PD-1 treatment in stage III melanoma.[Table: see text]

High dose bolus (HDB) interleukin-2 (IL2) and concurrent low dose ipilimumab followed sequentially by nivolumab in patients with advanced melanoma after failure of anti-PD1-based immunotherapy and BRAF-MEK inhibition.

9543 Background: Options are limited for patients with advanced metastatic melanoma who have disease progression following anti-PD1-based immunotherapy and BRAF-MEK inhibition (if BRAF V600 mutant). Evidence supports synergism between IL2 and CTLA4 blockade in enhancing the immunogenicity of the tumor microenvironment and therapeutic susceptibility to PD1 blockade. Methods: We conducted a phase II study of HDB IL2 in combination with LD ipilimumab followed sequentially by nivolumab in patients with advanced inoperable stage III or stage IV melanoma with progression after anti-PD1-based immunotherapy and BRAF-MEK inhibitors. Treatment consisted of up to 3 courses (One cycle is 21 days and one course is 4 cycles). HDB IL2 and concurrent ipilimumab 1 mg/kg were given during week 1 of the initial 2 cycles of each course. Nivolumab was given during week one of the 3rd cycle of each course. Patients without evidence of disease progression (RECIST v.1.1) or limiting toxicities (CTCAE v.5) were offered additional courses of treatment. A Simon two-stage minimax design (Simon, 1989) was followed. We report the outcomes for Stage I. Results: 12 pts (5 female, 7 male) with metastatic melanoma (2M1a, 1M1b, 6M1c, 3M1d) were treated. Median age 53 years (33 – 69), 11 cutaneous (including 1 acral) and 1 mucosal primary. Tumor mutation status: 4BRAF (V600E), 2NRAS (p.Q61K), 1NF1. The median number of prior regimens for metastatic melanoma was 3 (range 1 - 5). Eight patients previously received ipilimumab as monotherapy or in combination with anti-PD1. On study, the median number of doses of IL2 was 9 during cycle 1 and 7 during cycle 2. A median of 2 doses of ipilimumab and 1 dose of nivolumab were given as part of the combination regimen. Among the 11 evaluable patients (completed 1 course of systemic therapy), the response rate was 2/11 (18.2 %; 95% CI: 2.3% – 51.8%); 1CR, 1 PR, 5 SD, 4 PD and 1 NE as best response. After a median follow up of 39 months, both responses are ongoing (at 10+ and 37+ months), median progression free survival (PFS) was 3 months and median overall survival (OS) was 18.8 months. One-year PFS and OS were 17% (95% CI: 4.7% - 59%) and 83% (95% CI: 65% - 100%), respectively. The adverse event profile was consistent with the expected toxicity profile for each agent with no increase in frequency with the combination. Conclusions: Our combination regimen was relatively safe and well tolerated and demonstrated promising efficacy in a heavily pretreated patient population passing the prespecified efficacy criteria for Simon Stage I. The study has moved into Stage II testing. Clinical trial information: NCT04562129 .

Modeling Extraordinary Response Through Targeting Secondary Alterations in Fusion-Associated Sarcoma.

Targeted therapy in translocation-associated sarcomas has been limited to oncogenic activation of tyrosine kinases or ligands while gene fusions resulting in aberrant expression of transcription factors have been notoriously difficult to target. Moreover, secondary genetic alterations in sarcomas driven by translocations are uncommon, comprising mostly alterations in tumor suppressor genes (TP53, CDKN2A/B). Our study was triggered by an index patient showing a dramatic clinical response by targeting the secondary BRAF V600E mutation in a metastatic angiomatoid fibrous histiocytoma (AFH) harboring the typical EWSR1::CREB1 fusion. The patient, a 28-year-old female, was diagnosed with an AFH of the thigh and followed a highly aggressive clinical course, with rapid multifocal local recurrence within a year and widespread distant metastases (adrenal, bone, liver, lung). The tumor showed characteristic morphologic features, with histiocytoid cells intermixed with hemorrhagic cystic spaces and lymphoid aggregates. In addition to the pathognomonic EWSR1::CREB1 fusion, targeted DNA sequencing revealed in both primary and adrenal metastatic sites a hot spot BRAF V600E mutation and a CDKN2A/B deletion. Accordingly, the patient was treated with a BRAF-MEK inhibitor combination (encorafenib/binimetinib) showing an excellent but short-lived response. Using a CRISPR-Cas9 approach, we introduced the BRAF c.1799 T>A point mutation in human embryonic stem (hES) cells harboring a conditional EWSR1 (exon7)::CREB1 (exon7) translocation and further differentiated to mesenchymal progenitors (hES-MP) before fusion expression. The cells maintained the fusion transcript expression and the AFH core gene signature while responding to treatment with encorafenib and binimetinib. These results highlight that additional targeted DNA NGS in chemotherapy-resistant translocation-associated sarcomas may reveal actionable oncogenic drivers occurring as secondary genetic events during disease progression.

RICTOR/mTORC2 downregulation in BRAFV600E melanoma cells promotes resistance to BRAF/MEK inhibition.

The main drawback of BRAF/MEK inhibitors (BRAF/MEKi)-based targeted therapy in the management of BRAF-mutated cutaneous metastatic melanoma (MM) is the development of therapeutic resistance. We aimed to assess in this context the role of mTORC2, a signaling complex defined by the presence of the essential RICTOR subunit, regarded as an oncogenic driver in several tumor types, including MM. After analyzing The Cancer Genome Atlas MM patients' database to explore both overall survival and molecular signatures as a function of intra-tumor RICTOR levels, we investigated the effects of RICTOR downregulation in BRAFV600E MM cell lines on their response to BRAF/MEKi. We performed proteomic screening to identify proteins modulated by changes in RICTOR expression, and Seahorse analysis to evaluate the effects of RICTOR depletion on mitochondrial respiration. The combination of BRAFi with drugs targeting proteins and processes emerged in the proteomic screening was carried out on RICTOR-deficient cells in vitro and in a xenograft setting in vivo. Low RICTOR levels in BRAF-mutated MM correlate with a worse clinical outcome. Gene Set Enrichment Analysis of low-RICTOR tumors display gene signatures suggestive of activation of the mitochondrial Electron Transport Chain (ETC) energy production. RICTOR-deficient BRAFV600E cells are intrinsically tolerant to BRAF/MEKi and anticipate the onset of resistance to BRAFi upon prolonged drug exposure. Moreover, in drug-naïve cells we observed a decline in RICTOR expression shortly after BRAFi exposure. In RICTOR-depleted cells, both mitochondrial respiration and expression of nicotinamide phosphoribosyltransferase (NAMPT) are enhanced, and their pharmacological inhibition restores sensitivity to BRAFi. Our work unveils an unforeseen tumor-suppressing role for mTORC2 in the early adaptation phase of BRAFV600E melanoma cells to targeted therapy and identifies the NAMPT-ETC axis as a potential therapeutic vulnerability of low RICTOR tumors. Importantly, our findings indicate that the evaluation of intra-tumor RICTOR levels has a prognostic value in metastatic melanoma and may help to guide therapeutic strategies in a personalized manner.

BRAF-mutant microsatellite-stable rectal cancer with acquired KRAS mutation leading to drug resistance in liver metastasis

BRAF-mutant microsatellite-stable colorectal cancer (CRC), metastasized to distant sites, is associated with a poor prognosis. However, the BEACON CRC regimen, comprising a BRAF inhibitor, MEK inhibitor, and anti-EGFR antibody, offered a prolonged prognosis. Nonetheless, resistance to this regimen may occur, as observed in our reported case of CRC, where a KRAS mutation was identified in addition to the BRAF V600E mutation. Here, we present a case of 74-year-old woman with rectal cancer (pT4bN1bM0 Stage IIIc) harboring the BRAF V600E mutation. After resection of the primary tumor and during adjuvant chemotherapy using CAPOX (capecitabine and oxaliplatin), liver and lung metastases became apparent, and a companion diagnosis test revealed the presence of a BRAF V600E mutation. The new lesions were deemed resistant to the CAPOX regimen, and we decided to introduce encorafenib and cetuximab. After resection of liver metastases, encorafenib and cetuximab were reintroduced, but a new lesion appeared in hepatic S7, indicating resistance to the encorafenib and cetuximab regimen. The resistant liver metastasis was subsequently resected. To elucidate the resistance mechanism, we conducted a comprehensive analysis using the FoundationOne CDx cancer gene panel test, revealing the presence of a KRAS Q61H mutation alongside the BRAF V600E mutation. Subsequent liquid biopsy after liver recurrence confirmed the persistence of the KRAS Q61H mutation. Our results highlight the significance of cancer genome profiling tests (CGP tests) and liquid biopsies in guiding treatment strategies for BRAF-mutant colorectal cancer. Therefore, CGP testing offers valuable information for treatment, even if it does not lead to new drug administrations.

Abstract 7201: Targeting TAZ-TEAD in minimal residual disease enhances the duration of targeted therapy in melanoma models

Abstract Targeted therapies in cancer are limited by drug tolerance. In melanoma, tolerance to MAPK pathway inhibitors is associated with loss of SOX10 and enhanced YAP1/TAZ-TEAD activity. We show that loss of SOX10 is sufficient to up-regulate a TEAD transcriptional program with a strong dependence on TAZ. We developed a unique gene signature based on the transcriptomic changes following TAZ or YAP1 depletion. Expression of active TAZ was sufficient to mediate tolerance to BRAF inhibitors and MEK inhibitors. In WM983B cells, depletion of TAZ significantly reduced cell growth, whereas YAP1 knockdown resulted in little to no effect. These studies demonstrate that TAZ-TEAD activity plays an important role in melanoma drug tolerance and the development of acquired resistance. Citation Format: Connor A. Ott, Timothy Purwin, Manoela Tiago, Kristine Lou, Pan-Yu Chen, Somaneth Chowdhury, Glenn Mersky, Nir Hacohen, John Lamar, Claudia Capparelli, Gideon Bollag, Andrew Aplin. Targeting TAZ-TEAD in minimal residual disease enhances the duration of targeted therapy in melanoma 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 7201.

Treatment of Stage III Resectable Melanoma-Adjuvant and Neoadjuvant Approaches.

Patients with stage III resectable melanoma carry a high risk of melanoma recurrence that ranges from approximately 40% to 90% at 5 years following surgical management alone. Postoperative systemic adjuvant therapy targets residual micrometastatic disease that could be the source of future recurrence and death from melanoma. Randomized phase III adjuvant trials reported significant improvements in overall survival with high-dose interferon α in 2 of 3 studies (compared with observation and GMK ganglioside vaccine) and with anti-cytotoxic T-lymphocyte antigen 4 ipilimumab at 10 mg/kg compared with placebo and ipilimumab 3 mg/kg compared with high-dose interferon α. In the modern era, more recent phase III trials demonstrated significant recurrence-free survival improvements with anti-programmed cell death protein 1, pembrolizumab, and BRAF-MEK inhibitor combination dabrafenib-trametinib (for BRAF mutant melanoma) versus placebo. Furthermore, anti-programmed cell death protein 1, nivolumab and pembrolizumab have both been shown to significantly improve recurrence-free survival as compared with ipilimumab 10 mg/kg. For melanoma patients with clinically or radiologically detectable locoregionally advanced disease, emerging data support an important role for preoperative systemic neoadjuvant therapy. Importantly, a recent cooperative group trial (S1801) reported superior event-free survival rates with neoadjuvant versus adjuvant therapy. Collectively, current data from neoadjuvant immunotherapy and targeted therapy trials support a future change in clinical practice in favor of neoadjuvant therapy for eligible melanoma patients.