Target-Agnostic P-Glycoprotein Assessment Yields Strategies to Evade Efflux, Leading to a BRAF Inhibitor with Intracranial Efficacy

A critical review of RAF inhibitors in BRAF-mutated glioma treatment

BRAF gliomas have garnered significant attention in research due to the lack of effective treatments and their notable incidence, constituting 3% of all gliomas. This underlines the importance of investigating this area and the impact that targeted therapies could hold. This review discusses the development of targeted therapies for these tumors, examining the effectiveness of first-generation BRAF inhibitors such as Vemurafenib, Dabrafenib and Encorafenib, while addressing the challenges posed by paradoxical ERK activation. The advent of pan-RAF inhibitors, notably Tovorafenib, offers a promising advance, demonstrating enhanced efficacy and better penetration of the blood-brain barrier, without the issue of paradoxical activation. Nevertheless, continued research is essential to refine therapeutic strategies for BRAF-mutated gliomas, given the evolving nature of targeted therapy development.

Novel 4-Aryl-4H-chromene derivative displayed excellent in vivo anti-glioblastoma efficacy as the microtubule-targeting agent

In this study, a series of novel 4-Aryl-4H-chromene derivatives (D1-D31) were designed and synthesized by integrating quinoline heterocycle to crolibulin template molecule based on the strategy of molecular hybridization. One of these compounds D19 displayed positive antiproliferative activity against U87 cancer cell line (IC50 = 0.90 ± 0.03 μM). Compound D19 was verified as the microtubule-targeting agent through downregulating tubulin related genes of U87 cells, destroying the cytoskeleton of tubulins and interacting with the colchicine-binding site to inhibit the polymerization of tubulins by transcriptome analysis, immune-fluorescence staining, microtubule dynamics and EBI competition assays as well as molecular docking simulations. Moreover, compound D19 induced G2/M phase arrest, resulted in cell apoptosis and inhibited the migration of U87 cells by flow cytometry analysis and wound healing assays. Significantly, compound D19 dose-dependently inhibited the tumor growth of orthotopic glioma xenografts model (GL261-Luc) and effectively prolonged the survival time of mice, which were extremely better than those of positive drug temozolomide (TMZ). Compound D19 exhibited potent in vivo antivascular activity as well as no observable toxicity. Furthermore, the results of in silico simulation studies and P-gp transwell assays verified the positive correlation between compound D19's Blood-Brain Barrier (BBB) permeability and its in vivo anti-GBM activity. Overall, compound D19 can be used as a promising anti-GBM lead compound for the treatment of glioblastoma.

Brain metastases and next-generation anticancer therapies: a survival guide for clinicians

Historically, patients with brain metastases (BMs) have been characterized by few systemic treatment options and poor prognosis. The recent introduction of next-generation anticancer therapies such as molecular targeted agents and immunotherapy have revolutionized the clinical decision-making process of this sub-population, posing new challenges to physicians. In this review, current evidence for the use of checkpoint inhibitors and targeted therapies in patients with BMs are discussed, with a focus on lung cancer, breast cancer, melanoma and renal cell carcinoma, providing suggestions and potential workflows for daily clinical practice. Several other on-going and future challenges, such as clinical trials design, ways to improve CNS penetration of novel drugs and unique molecular characteristics of BMs, are also discussed. The aim is producing an updated and easy-to-read guide for physicians, to improve decision-making in clinical practice.

Recent Advances in Pyrimidine-Based Drugs

Pyrimidines have become an increasingly important core structure in many drug molecules over the past 60 years. This article surveys recent areas in which pyrimidines have had a major impact in drug discovery therapeutics, including anti-infectives, anticancer, immunology, immuno-oncology, neurological disorders, chronic pain, and diabetes mellitus. The article presents the synthesis of the medicinal agents and highlights the role of the biological target with respect to the disease model. Additionally, the biological potency, ADME properties and pharmacokinetics/pharmacodynamics (if available) are discussed. This survey attempts to demonstrate the versatility of pyrimidine-based drugs, not only for their potency and affinity but also for the improved medicinal chemistry properties of pyrimidine as a bioisostere for phenyl and other aromatic π systems. It is hoped that this article will provide insight to researchers considering the pyrimidine scaffold as a chemotype in future drug candidates in order to counteract medical conditions previously deemed untreatable.

Belvarafenib penetrates the BBB and shows potent antitumor activity in a murine melanoma brain metastasis model

Brain metastasis is a common complication in melanoma patients with BRAF and NRAS mutations and has a poor prognosis. Although BRAF inhibitors are clinically approved, their poor brain penetration limits their efficacy in brain metastasis. Thus, melanoma brain metastasis still requires better treatment. Belvarafenib, a pan-RAF inhibitor, has reported antitumor activity in melanoma with RAF and RAS mutations in animal models and patients. However, brain permeability and antitumor efficacy on brain metastasis have not been determined. This study confirmed the brain penetration of belvarafenib, the antitumor activity on BRAF and NRAS mutant melanoma, and the efficacy on melanoma within the brain. Belvarafenib strongly suppressed melanoma in BRAF V600E mutant A375SM tumor-bearing mice. It also significantly inhibited tumor growth in NRAS mutant SK-MEL-30 and K1735 tumor-bearing mice and synergized to enhance the antitumor activity combined with cobimetinib or atezolizumab. Belvarafenib was penetrated at considerable levels into the brains of mice and rats following oral administration. The exposure of belvarafenib in the brain was similar to or higher than that in plasma, and this high brain penetration differed significantly from that of other BRAF inhibitors with low brain penetration. Most importantly, belvarafenib strongly reduced tumor burden and markedly improved survival benefits in mice intracranially implanted with A375SM melanoma. These results demonstrated that belvarafenib, which has favorable BBB permeability, and potent antitumor activity on the tumors with BRAF/NRAS mutations, may be a promising therapeutic option for patients with BRAF/NRAS mutant melanoma brain metastasis.

BRAF-mediated brain tumors in adults and children: A review and the Australian and New Zealand experience

The mitogen-activated protein kinase (MAPK) pathway signaling pathway is one of the most commonly mutated pathways in human cancers. In particular, BRAF alterations result in constitutive activation of the rapidly accelerating fibrosarcoma-extracellular signal-regulated kinase-MAPK significant pathway, leading to cellular proliferation, survival, and dedifferentiation. The role of BRAF mutations in oncogenesis and tumorigenesis has spurred the development of targeted agents, which have been successful in treating many adult cancers. Despite advances in other cancer types, the morbidity and survival outcomes of patients with glioma have remained relatively stagnant. Recently, there has been recognition that MAPK dysregulation is almost universally present in paediatric and adult gliomas. These findings, accompanying broad molecular characterization of gliomas, has aided prognostication and offered opportunities for clinical trials testing targeted agents. The use of targeted therapies in this disease represents a paradigm shift, although the biochemical complexities has resulted in unexpected challenges in the development of effective BRAF inhibitors. Despite these challenges, there are promising data to support the use of BRAF inhibitors alone and in combination with MEK inhibitors for patients with both low-grade and high-grade glioma across age groups. Safety and efficacy data demonstrate that many of the toxicities of these targeted agents are tolerable while offering objective responses. Newer clinical trials will examine the use of these therapies in the upfront setting. Appropriate duration of therapy and durability of response remains unclear in the glioma patient cohort. Longitudinal efficacy and toxicity data are needed. Furthermore, access to these medications remains challenging outside of clinical trials in Australia and New Zealand. Compassionate access is limited, and advocacy for mechanism of action-based drug approval is ongoing.

Phase I dose-escalation study of procaspase-activating compound-1 in combination with temozolomide in patients with recurrent high-grade astrocytomas

BACKGROUND

Procaspase-3 (PC-3) is overexpressed in various tumor types, including gliomas. Targeted PC-3 activation combined with chemotherapy is a novel strategy for treating patients with high-grade gliomas, with promising preclinical activity. This study aimed to define safety and tolerability of procaspase-activating compound-1 (PAC-1) in combination with temozolomide (TMZ) for patients with recurrent high-grade astrocytomas.

METHODS

A modified-Fibonacci dose-escalation 3 + 3 design was used. PAC-1 was administered at increasing dose levels (DL; DL1 = 375 mg) on days 1-21, in combination with TMZ 150 mg/m2/5 days, per 28-day cycle. Dose-limiting toxicity was assessed during the first 2 cycles. Neurocognitive function (NCF) testing was conducted throughout the study.

RESULTS

Eighteen patients were enrolled (13 GBM, IDH-wild type; 2 astrocytoma, IDH-mutant, grade 3; 3 astrocytoma, IDH-mutant, grade 4). Dose escalation was discontinued after DL3 (ie, PAC-1, 625 mg) due to lack of additional funding. Grade 3 toxicity was observed in 1 patient at DL1 (elevated liver transaminases) and 1 at DL 2 (headache). Two partial responses were observed at DL1 in patients with GBM, O6-methylguanine-DNA methyltransferase (MGMT) promoter methylated. Two patients had stable disease, and 11 experienced progression. NCF testing did not show a clear relationship between PAC-1 dose, treatment duration, and declines in NCF.

CONCLUSIONS

Combination of PAC-1 and TMZ was well tolerated up to 625 mg orally daily and TMZ orally 150 mg/m2/5 days per 28-day cycle. The maximum tolerated dose was not reached. Further dose escalation of PAC-1 in combination with TMZ is advised before conducting a formal prospective efficacy study in this patient population.