The ERK inhibitor LY3214996 augments anti-PD-1 immunotherapy in preclinical mouse models of BRAFV600E melanoma brain metastasis

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment; however, only a subset of patients with brain metastasis (BM) respond to ICI. Activating mutations in the mitogen-activated protein kinase signaling pathway are frequent in BM. The objective of this study was to evaluate whether therapeutic inhibition of extracellular signal-regulated kinase (ERK) can improve the efficacy of ICI for BM.

METHODS

We used immunotypical mouse models of BM bearing dual extracranial/intracranial tumors to evaluate the efficacy of single-agent and dual-agent treatment with selective ERK inhibitor LY3214996 (LY321) and anti-programmed death receptor 1 (PD-1) antibody. We verified target inhibition and drug delivery, then investigated treatment effects on T-cell response and tumor-immune microenvironment using high-parameter flow cytometry, multiplex immunoassays, and T-cell receptor profiling.

RESULTS

We found that dual treatment with LY321 and anti-PD-1 significantly improved overall survival in 2 BRAFV600E-mutant murine melanoma models but not in KRAS-mutant murine lung adenocarcinoma. We demonstrate that although LY321 has limited blood-brain barrier (BBB) permeability, combined LY321 and anti-PD-1 therapy increases tumor-infiltrating CD8+ effector T cells, broadens the T-cell receptor repertoire in the extracranial tumor, enriches T-cell clones shared by the periphery and brain, and reduces immunosuppressive cytokines and cell populations in tumors.

CONCLUSIONS

Despite the limited BBB permeability of LY321, combined LY321 and anti-PD-1 treatment can improve intracranial disease control by amplifying extracranial immune responses, highlighting the role of extracranial tumors in driving intracranial response to treatment. Combined ERK and PD-1 inhibition is a promising therapeutic approach, worthy of further investigation for patients with melanoma BM.

Leveraging translational insights toward precision medicine approaches for brain metastases

Due to increasing incidence and limited treatments, brain metastases (BM) are an emerging unmet need in modern oncology. Development of effective therapeutics has been hindered by unique challenges. Individual steps of the brain metastatic cascade are driven by distinctive biological processes, suggesting that BM possess intrinsic biological differences compared to primary tumors. Here, we discuss the unique physiology and metabolic constraints specific to BM as well as emerging treatment strategies that leverage potential vulnerabilities.

DDDR-05. ERK INHIBITION INCREASES SENSITIVITY TO ANTI-PD-1 THERAPY IN A MOUSE MODEL OF BRAF MUTANT MELANOMA BRAIN METASTASIS

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized the landscape of cancer treatment, including brain metastases. However, only a subset of patients with brain metastases respond to ICI. Activating mutations in the mitogen-activated protein kinase (MAPK) signaling pathway, a key regulator of cell processes, are frequently found in brain metastases. LY3214996 (LY321) is a selective ERK 1/2 inhibitor that inhibits MAPK signaling and leads to regression of extracranial disease in preclinical models. Our objective was to evaluate whether with ERK inhibition (ERKi) can improve the efficacy of ICI in preclinical models of brain metastases.

METHODS

We tested sensitivity to LY321 in a BRAFV600E mutant, ICI resistant murine melanoma cell line (D4M) both in vitro and in vivo. To model brain metastases in vivo, we implanted D4M cells subcutaneously with subsequent intracranial implantation three days later. The treatment arms included LY321 and anti-PD-1 combination therapy, single agent therapies, and respective controls. We tested the efficacies of 2-week versus 4-week LY321 treatments, as well as 3-week treatment in an independent experiment.

RESULTS

D4M demonstrates in vitro sensitivity to LY321 (IC50 value of 4.75 µM). Our model demonstrated that LY321 in combination with anti-PD-1 improves both intracranial and extracranial disease control. Increased survival with combination therapy was observed with 3-week and 4-week LY321 administration. While individually, LY321 and anti-PD-1 produced better survival outcomes than control groups, combination therapy significantly outperformed both monotherapies.

CONCLUSION

Previous studies demonstrated that LY321 has minimal intracranial activity. However, we found that ERKi reduces intracranial tumor burden, with improved efficacy in combination with ICI in immunocompetent mice. Together, these data suggest that ERKi increases sensitivity to ICI therapy in pre-clinical brain metastasis models. Further investigation is needed to elucidate the mechanisms of this therapeutic approach, and to ultimately determine whether this combination will improve patient outcomes.

Activity of Adagrasib (MRTX849) in Brain Metastases: Preclinical Models and Clinical Data from Patients with KRASG12C-Mutant Non-Small Cell Lung Cancer

PURPOSE

Patients with KRAS-mutant non-small cell lung cancer (NSCLC) with brain metastases (BM) have a poor prognosis. Adagrasib (MRTX849), a potent oral small-molecule KRASG12C inhibitor, irreversibly and selectively binds KRASG12C, locking it in its inactive state. Adagrasib has been optimized for favorable pharmacokinetic properties, including long half-life (∼24 hours), extensive tissue distribution, dose-dependent pharmacokinetics, and central nervous system penetration; however, BM-specific antitumor activity of KRASG12C inhibitors remains to be fully characterized.

EXPERIMENTAL DESIGN

A retrospective database query identified patients with KRAS-mutant NSCLC to understand their propensity to develop BM. Preclinical studies assessed physiochemical and pharmacokinetic properties of adagrasib. Mice bearing intracranial KRASG12C-mutant NSCLC xenografts (LU99-Luc/H23-Luc/LU65-Luc) were treated with clinically relevant adagrasib doses, and levels of adagrasib in plasma, cerebrospinal fluid (CSF), and brain were determined along with antitumor activity. Preliminary clinical data were collected from 2 patients with NSCLC with untreated BM who had received adagrasib 600 mg twice daily in the phase Ib cohort of the KRYSTAL-1 trial; CSF was collected, adagrasib concentrations measured, and antitumor activity in BM evaluated.

RESULTS

Patients with KRAS-mutant NSCLC demonstrated high propensity to develop BM (≥40%). Adagrasib penetrated into CSF and demonstrated tumor regression and extended survival in multiple preclinical BM models. In 2 patients with NSCLC and untreated BM, CSF concentrations of adagrasib measured above the target cellular IC50. Both patients demonstrated corresponding BM regression, supporting potential clinical activity of adagrasib in the brain.

CONCLUSIONS

These data support further development of adagrasib in patients with KRASG12C-mutant NSCLC with untreated BM. See related commentary by Kommalapati and Mansfield, p. 3179.

Racial, ethnic, and gender diversity of applicants and matriculants to neurological surgery residency programs

OBJECTIVE

The aim of this study was to identify trends in the demographic constitution of applicants and matriculants to neurological surgery based on race, ethnicity, and gender.

METHODS

The authors conducted a cross-sectional study using compiled demographic data obtained from the Association of American Medical Colleges. Trends analyzed included proportional changes in race, ethnicity, and gender of applicants and matriculants to neurosurgical residency programs from academic years 2010-2011 to 2018-2019.

RESULTS

A total of 5100 applicants and 2104 matriculants to neurosurgical residency programs were analyzed. No significant change in the percentage of overall women applicants (+0.3%, 95% CI -0.7% to 1.3%; p = 0.77) or in the percentage of women matriculants (+0.3%, 95% CI -2.2% to 2.9%; p = 0.71) was observed. For applicants, no change over time was observed in the percentages of American Indian or Alaska Native (AI/AN) men (0.0%, 95% CI -0.3% to 0.3%; p = 0.65); Asian men (-0.1%, 95% CI -1.2% to 1.1%; p = 0.97); Black or African American men (-0.2%, 95% CI -0.7% to 0.4%; p = 0.91); Hispanic, Latino, or of Spanish Origin men (+0.4%, 95% CI -0.8% to 1.7%; p = 0.26); White men (+0.5%, 95% CI -2.1% to 3.0%; p = 0.27); Asian women (+0.1,% 95% CI -0.9% to 1.1%; p = 0.73); Black or African American women (0.0%, 95% CI -0.6% to 0.5%; p = 0.30); Hispanic, Latino, or of Spanish Origin women (0.0%, 95% CI -0.4% to 0.4%; p = 0.71); and White women (+0.3%, 95% CI -1.1% to 1.7%; p = 0.34). For matriculants, no change over time was observed in the percentages of AI/AN men (0.0%, 95% CI -0.6% to 0.6%; p = 0.56); Asian men (0.0%, 95% CI -2.7% to 2.7%; p = 0.45); Black or African American men (-0.3%, 95% CI -1.4% to 0.8%; p = 0.52); Hispanic, Latino, or of Spanish Origin men (+0.6%, 95% CI -0.8 to 2.0%; p = 0.12); White men (-1.0%, 95% CI -5.3% to 3.3%; p = 0.92); Asian women (+0.1%, 95% CI -1.3% to 1.5%; p = 0.85); Black or African American women (0.0%, 95% CI -0.6% to 0.7%; p = 0.38); Hispanic, Latino, or of Spanish Origin women (-0.1%, 95% CI -0.7% to 0.5%; p = 0.46); and White women (+0.3%, 95% CI -2.4% to 3.0%; p = 0.70).

CONCLUSIONS

Despite efforts to diversify the demographic constitution of incoming neurosurgical trainees, few significant advances have been made in recent years. This study suggests that improved strategies for recruitment and cultivating early interest in neurological surgery are required to further increase the diversification of future cohorts of neurosurgical trainees.

Emerging Systemic Treatment Perspectives on Brain Metastases: Moving Toward a Better Outlook for Patients

The diagnosis of brain metastases has historically been a dreaded, end-stage complication of systemic disease. Additionally, with the increasing effectiveness of systemic therapies that prolong life expectancy and improved imaging tools, the incidence of intracranial progression is becoming more common. Within this context, there has been increasing attention directed at understanding the molecular underpinnings of intracranial progression. Exploring the unique features of brain metastases compared with their extracranial counterparts to identify aberrant signaling pathways, which can be targeted pharmacologically, may help lead to new treatments for this patient population. Additionally, critical discoveries outside the sphere of the central nervous system are increasingly being applied to brain metastases with the emergence of immune checkpoint inhibition, becoming a prevalent treatment option for patients with brain metastases across multiple histologies. As novel treatment strategies are considered, they require thoughtful incorporation of agents that can cross the blood-brain barrier and can synergize with pre-existing agents through rational combinations. Lastly, as clinicians and scientists continue to understand key molecular features of these tumors, they will continue to influence the treatment algorithms that are developing for the management of these patients. Due to the complexity of treatment decisions for patients with brain metastases, an emerging tool is the utilization of multidisciplinary brain metastasis tumor boards to ensure optimal treatment decisions are made and that patients are provided access to applicable clinical trials. Looking to the future, the collective effort to understand the various tumor-intrinsic and tumor-extrinsic factors that promote central nervous system seeding and propagation will have the potential to change the clinical trajectory for these patients.

Central Nervous System Metastases

The proportion of patients developing central nervous system (CNS) metastasis is increasing. Most are identified once symptomatic. Surgical resection is indicated for solitary or symptomatic brain metastases, separation surgery for compressive radioresistant spinal metastases, and instrumentation for unstable spinal lesions. Surgical biopsies are performed when histological diagnoses are required. Stereotactic radiosurgery is an option for limited small brain metastases and radioresistant spinal metastases. Whole-brain radiotherapy is reserved for extensive brain metastases and leptomeningeal disease with approaches to reduce cognitive side effects. Radiosensitive and inoperable spinal metastases typically receive external beam radiotherapy. Systemic therapy is increasingly being utilized for CNS metastases.

United States Medicolegal Progress and Innovation in Telemedicine in the Age of COVID-19: A Primer for Neurosurgeons

Telemedicine has received increased attention in recent years as a potential solution to expand clinical capability and patient access to care in many fields, including neurosurgery. Although patient and physician attitudes are rapidly shifting toward greater telemedicine use in light of the COVID-19 pandemic, there remains uncertainty about telemedicine's regulatory future. Despite growing evidence of telemedicine's utility, there remain a number of significant medicolegal barriers to its mass adoption and wider implementation. Herein, we examine recent progress in state and federal regulations in the United States governing telemedicine's implementation in quality of care, finance and billing, privacy and confidentiality, risk and liability, and geography and interstate licensure, with special attention to how these concern teleneurosurgical practice. We also review contemporary topics germane to the future of teleneurosurgery, including the continued expansion of reciprocity in interstate licensure, expanded coverage for homecare services for chronic conditions, expansion of Center for Medicare and Medicaid Services reimbursements, and protections of store-and-forward technologies. Additionally, we discuss recent successes in teleneurosurgery, stroke care, and rehabilitation as models for teleneurosurgical best practices. As telemedicine technology continues to mature and its expanse grows, neurosurgeons' familiarity with its benefits, limitations, and controversies will best allow for its successful adoption in our field to maximize patient care and outcomes.

Prognostic Value of Hemorrhagic Brainstem Injury on Early Computed Tomography: A TRACK-TBI Study

BACKGROUND

Traumatic brainstem injury has yet to be incorporated into widely used imaging classification systems for traumatic brain injury (TBI), and questions remain regarding prognostic implications for this TBI subgroup. To address this, retrospective data on patients from the multicenter prospective Transforming Research and Clinical Knowledge in TBI study were studied.

METHODS

Patients with brainstem and cerebrum injury (BSI+) were matched by age, sex, and admission Glasgow Coma Scale (GCS) score to patients with cerebrum injuries only. All patients had an interpretable head computed tomography (CT) scan from the first 48 hours after injury and a 6-month Glasgow Outcome Scale Extended (GOSE) score. CT scans were reviewed for brainstem lesions and, when present, characterized by location, size, and type (traumatic axonal injury, contusion, or Duret hemorrhage). Clinical, demographic, and outcome data were then compared between the two groups.

RESULTS

Mann-Whitney U-tests showed no significant difference in 6-month GOSE scores in patients with BSI+ (mean 2.7) compared with patients with similar but only cerebrum injuries (mean 3.9), although there is a trend (p = 0.10). However, subclassification by brainstem lesion type, traumatic axonal injury (mean 4.0) versus Duret hemorrhage or contusion (mean 1.4), did identify a proportion of BSI+ with significantly less favorable outcome (p = 0.002). The incorporation of brainstem lesion type (traumatic axonal injury vs. contusion/Duret), along with GCS into a multivariate logistic regression model of favorable outcome (GOSE score 4-8) did show a significant contribution to the prognostication of this brainstem injury subgroup (odds ratio 0.08, 95% confidence interval 0.00-0.67, p = 0.01).

CONCLUSIONS

These findings suggest two groups of patients with brainstem injuries may exist with divergent recovery potential after TBI. These data support the notion that newer CT imaging classification systems may augment traditional clinical measures, such as GCS in identifying those patients with TBI and brainstem injuries that stand a higher chance of favorable outcome.

HIF1A signaling selectively supports proliferation of breast cancer in the brain

Blood-borne metastasis to the brain is a major complication of breast cancer, but cellular pathways that enable cancer cells to selectively grow in the brain microenvironment are poorly understood. We find that cultured circulating tumor cells (CTCs), derived from blood samples of women with advanced breast cancer and directly inoculated into the mouse frontal lobe, exhibit striking differences in proliferative potential in the brain. Derivative cell lines generated by serial intracranial injections acquire selectively increased proliferative competency in the brain, with reduced orthotopic tumor growth. Increased Hypoxia Inducible Factor 1A (HIF1A)-associated signaling correlates with enhanced proliferation in the brain, and shRNA-mediated suppression of HIF1A or drug inhibition of HIF-associated glycolytic pathways selectively impairs brain tumor growth while minimally impacting mammary tumor growth. In clinical specimens, brain metastases have elevated HIF1A protein expression, compared with matched primary breast tumors, and in patients with brain metastases, hypoxic signaling within CTCs predicts decreased overall survival. The selective activation of hypoxic signaling by metastatic breast cancer in the brain may have therapeutic implications.

Changing How Race Is Portrayed in Medical Education: Recommendations From Medical Students

The medical community has been complicit in legitimizing claims of racial difference throughout the history of the United States. Unfortunately, a rigorous examination of the role medicine plays in perpetuating inequity across racial lines is often missing in medical school curricula due to time constraints and other challenges inherent to medical education. The imprecise use of race-a social construct-as a proxy for pathology in medical education is a vestige of institutionalized racism. Recent examples are presented that illustrate how attributing outcomes to race may contribute to bias and unequal care. This paper proposes the following recommendations for guiding efforts to mitigate the adverse effects associated with the use of race in medical education: emphasize the need for incoming students to be familiar with how race can influence health outcomes; provide opportunities to hold open conversations about race in medicine among medical school faculty, students, and staff; craft and implement protocols that address and correct the inappropriate use of race in medical school classes and course materials; and encourage a large cultural shift within the field of medicine. Adoption of an interdisciplinary approach that taps into many fields, including ethics, history, sociology, evolutionary genetics, and public health is a necessary step for cultivating more thoughtful physicians who will be better prepared to care for patients of all racial and ethnic backgrounds.

Trends in Race/Ethnicity Among Applicants and Matriculants to US Surgical Specialties, 2010-2018

IMPORTANCE

Surgical programs across the US continue to promote and invest in initiatives aimed at improving racial/ethnic diversity, but whether this translates to changes in the percentage of applicants or matriculants from racial/ethnic minority groups remains unclear.

OBJECTIVE

To examine trends in the percentage of applicants and matriculants to US surgical specialties who identified as part of a racial/ethnic group underrepresented in medicine from the 2010-2011 to 2018-2019 academic years.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study examined trends in self-reported racial/ethnic identity among applicants and matriculants to US residency programs to evaluate demographic changes among surgical programs from 2010 to 2018. Data were obtained from the Association of American Medical Colleges.

RESULTS

The study population consisted of a total of 737 034 applicants and 265 365 matriculants to US residency programs, including 134 158 applicants and 41 347 matriculants to surgical programs. A total of 21 369 applicants (15.9%) and 5704 matriculants (13.8%) to surgical specialties identified as underrepresented in medicine. There was no statistically significant difference in the percentage of applicants underrepresented in medicine based on race/ethnicity for all surgical specialties combined in 2010 vs 2018 (15.3% [95% CI, 14.7%-15.9%] vs 17.5% [95% CI, 16.9%-18.1%]; P = .63). Thoracic surgery was the only surgical specialty in which there was a statistically significant change in the percentage of applicants (8.1% [95% CI, 4.9%-13.2%] vs 14.6% [95% CI, 10.2%-20.4%]; P = .02) or matriculants (0% [95% CI, 0%-19.4%] vs 10.0% [95% CI, 4.0%-23.1%]; P = .01) underrepresented in medicine based on race/ethnicity. Obstetrics and gynecology had the highest mean percentage of applicants (20.2%; 95% CI, 19.4%-20.8%) and matriculants (19.0%; 95% CI, 18.2%-19.8%) underrepresented in medicine among surgical specialties. Thoracic surgery had the lowest mean percentage of applicants (12.5%; 95% CI, 9.46%-15.4%) and otolaryngology the lowest mean percentage of matriculants (8.5%; 95% CI, 7.2%-9.9%) underrepresented in medicine.

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, overall US surgical programs had no change in the percentage of applicants or matriculants who self-identified as underrepresented in medicine based on race/ethnicity, but the proportion remained higher than in nonsurgical specialties. Reevaluation of current strategies aimed at increasing racial/ethnic representation appear to be necessary to help close the existing gap in medicine and recruit a more racially/ethnically diverse surgical workforce.

Ongoing challenges in access to diabetes care among the indigenous population: perspectives of individuals living in rural Guatemala

Background

Indigenous persons living in Latin America suffer from a higher prevalence of type 2 diabetes compared to their non-indigenous counterparts. This difference has been attributed to a wide range of factors. Future interventions could be influenced by a deeper understanding of the challenges that impact care in rural regions and in other low-income settings.

Methods

This study was conducted using a modified grounded theory approach. Extended observations and fifteen interviews were performed with adult male and female residents of three rural Mayan towns in Sololá Department, Guatemala using purposive sampling. Questions focused on the perceptions of individuals living with type 2 diabetes and their caregivers regarding disease and treatment.

Results

Across interviews the most common themes that emerged included mistreatment by healthcare providers, mental health comorbidity, and medication affordability. These perceptions were in part influenced by indigeneity, poverty, and/or gender.

Conclusions

Both structural and cultural barriers continue to impact diabetes care for indigenous communities in rural Guatemala. The interviews in this study suggest that indigenous people experience mistrust in the health care system, unreliable access to care, and mental health comorbidity in the context of type 2 diabetes care. These experiences are shaped by the complex relationship among poverty, gender, and indigeneity in this region. Targeted interventions that are conscious of these factors may increase their chances of success when attempting to address similar health disparities in comparable populations.