Phase I LITESPARK-001 study of belzutifan for advanced solid tumors: Extended 41-month follow-up in the clear cell renal cell carcinoma cohort

Casdatifan (AB521) is a novel and potent allosteric small molecule inhibitor of protumourigenic HIF-2α dependent transcription

BACKGROUND AND PURPOSE

Hypoxia-inducible factor 2α (HIF-2α) is a transcription factor that mediates the expression of genes critical for cell adaptation and survival in low oxygen (hypoxic) conditions. In cancer, hypoxic conditions or molecular alterations within cancer cells can lead to HIF-2α accumulation and promote tumour growth and progression. Inactivating mutations in the von Hippel-Lindau (VHL) gene disable the oxygen-dependent HIF-2α degradation pathway and cause constitutive HIF-2α activity. VHL mutations are prevalent in clear cell renal cell carcinoma (ccRCC) where HIF-2α is a known tumourigenic driver. HIF-2α inhibition was shown to improve ccRCC patient outcomes clinically, warranting development of next-generation inhibitors.

EXPERIMENTAL APPROACH

Pharmacological effects of a novel small molecule allosteric inhibitor of HIF-2α, AB521 (casdatifan), were evaluated using in vitro cell-based assays and in vivo mouse models.

KEY RESULTS

AB521 inhibited HIF-2α-mediated transcription in cancer cells, endothelial cells, and M2-polarised macrophages. AB521 was selective for HIF-2α, displaying no activity against HIF-1α, and did not exhibit off-target cytotoxicity. When delivered orally to mice, AB521 caused dose-dependent decreases in HIF-2α-associated pharmacodynamic markers and significant regression of human ccRCC xenograft tumours. AB521 combined favourably with cabozantinib, a standard of care tyrosine kinase inhibitor, or zimberelimab, a clinical-stage anti-PD-1 antibody, in ccRCC xenograft studies.

CONCLUSIONS AND IMPLICATIONS

AB521 is a potent, selective and orally bioavailable HIF-2α inhibitor, with favourable pharmacological properties, that is being explored clinically for the treatment of ccRCC.

Belzutifan for von Hippel-Lindau disease-associated renal cell carcinoma and other neoplasms (LITESPARK-004): 50 months follow-up from a single-arm, phase 2 study

BACKGROUND

Hypoxia-inducible factor-2α inhibitor belzutifan is approved for von Hippel-Lindau disease-associated renal cell carcinoma, CNS haemangioblastomas, and pancreatic neuroendocrine tumours, based on previously published initial results from the LITESPARK-004 study. Updated results are presented here after a median follow-up of nearly 50 months.

METHODS

In this single-arm, phase 2 study, participants were enrolled at 11 centres in Denmark, France, the UK, and the USA. Oral belzutifan 120 mg once daily was given to eligible adults aged 18 years or older with a diagnosis of von Hippel-Lindau disease (based on germline VHL alterations), at least one measurable renal cell carcinoma tumour, no tumour larger than 3 cm that necessitated immediate surgery, no metastatic disease, no previous systemic anticancer treatment, and an Eastern Cooperative Oncology Group performance status score of 0 or 1. The primary endpoint was the proportion of participants with an objective response in von Hippel-Lindau disease-associated renal cell carcinoma per Response Evaluation Criteria in Solid Tumours, version 1.1, determined by an independent review committee, and assessed in all participants who received at least one dose of belzutifan. This ongoing study is no longer recruiting and is registered at ClinicalTrials.gov, NCT03401788.

FINDINGS

Between May 31, 2018, and Mar 29, 2019, 61 participants were enrolled; 36 (59%) were continuing treatment as of April 3, 2023. The median age of all enrolled participants was 41·0 years (IQR 29·0-51·0); 32 (52%) of 61 participants were male and 29 (48%) were female; most were White (n=55; 90%). Median study follow-up was 49·9 months (IQR 48·9-52·2). 41 (67%; 95% CI 54-79) of 61 participants with renal cell carcinoma had an objective response; seven (11%) had a complete response and 34 (56%) a partial response. 13 grade 3 treatment-related adverse events occurred in 11 (18%) participants (anaemia: seven [11%]; fatigue: three [5%]; urinary tract infection: one [2%]; hypoxia: one [2%]; and blister: one [2%]). None of the participants had a grade 4 or 5 treatment-related adverse event. Four (7%) participants had serious treatment-related adverse events (one participant each: anaemia, urinary tract infection, intracranial haemorrhage, and hypoxia).

INTERPRETATION

Updated results support the use of belzutifan as systemic treatment for von Hippel-Lindau disease-associated renal cell carcinoma.

FUNDING

Merck Sharp & Dohme, a subsidiary of Merck & Co, Rahway, NJ, USA; the Intramural Research Program of the National Institutes of Health, National Cancer Institute Center for Cancer Research; and a grant from the National Cancer Institute.

A Practical Guide for the Management of Toxicities Associated with Belzutifan

Belzutifan offers a significant therapeutic advance for von Hippel-Lindau-associated and advanced renal cell carcinoma but is associated with notable toxicities, particularly anemia and hypoxia. Effective management requires vigilant monitoring, timely interventions, and dose adjustments.

Biomarker-informed care for patients with renal cell carcinoma

Kidney cancer is a commonly diagnosed cancer in adults, and clear cell renal cell carcinoma (ccRCC) is the most common histological subtype. Immune checkpoint inhibitors have revolutionized care for patients with ccRCC, either as adjuvant therapy or combined with other agents in advanced disease. However, biomarkers to predict therapeutic benefits are lacking. Here, we explore biomarkers that predict therapeutic response in other tumor types and discuss the reasons for their ineffectiveness in ccRCC. We also review emerging predictive and prognostic biomarkers to prioritize in ccRCC, including gene expression signatures.

Resistance to immunotherapy in non-small cell lung cancer: Unraveling causes, developing effective strategies, and exploring potential breakthroughs

Over the last two decades, advancements in deciphering the intricate interactions between oncology and immunity have fueled a meteoric rise in immunotherapy for non-small cell lung cancer, typified by an explosive growth of immune checkpoint inhibitors. However, resistance to immunotherapy remains inevitable. Herein we unravel the labyrinthine mechanisms of resistance to immunotherapy, characterized by their involvement of nearly all types of cells within the body, beyond the extrinsic cancer cells, and importantly, such cells are not only (inhibitory or excitatory, or both) signal recipients but also producers, acting in a context-dependent manner. At the molecular level, these mechanisms underlie genetic and epigenetic aberrations, which are regulated by or regulate various protein kinases, growth factors, and cytokines with inherently dynamic and spatially heterogeneous properties. Additionally, macroscopic factors such as nutrition, comorbidities, and the microbiome within and around organs or tumor cells are involved. Therefore, developing therapeutic strategies combined with distinct action informed by preclinical, clinical, and real-world evidence, such as radiotherapy, chemotherapy, targeted therapy, antibody-drug conjugates, oncolytic viruses, and cell-based therapies, may stand as a judicious reality, although the ideality is to overcome resistance point-by-point through a novel drug. Notably, we highlight a realignment of treatment aims, moving the primary focus from eliminating cancer cells -- such as through chemotherapy and radiotherapy -- to promoting immune modulation and underscore the value of regulating various components within the host macro- or micro-environment, as their effects, even if seemingly minimal, can cumulatively contribute to visible clinical benefit when applied in combination with ICIs. Lastly, this review also emphasizes the current hurdles scattered throughout preclinical and clinical studies, and explores evolving directions in the landscape of immunotherapy for NSCLC.

Belzutifan for the treatment of renal cell carcinoma

Belzutifan received its first FDA approval in 2021 for treating clinical manifestations of von Hippel-Lindau (VHL) disease including renal cell carcinoma (RCC) followed by approval in 2023 for treating advanced sporadic RCC that has progressed through multiple lines of treatment. It is the first FDA-approved drug to target hypoxia-inducible factor 2 alpha (HIF-2α). By inhibiting the HIF-2α transcription factor, belzutifan prevents HIF-2α from dimerizing with HIF-1β, thereby preventing the transcription of downstream oncogenes. Most clear cell renal cell carcinoma (ccRCC) tumors are associated with VHL deletion or inactivation resulting in HIF-2α overexpression that represents a key contributor to tumorigenesis, thereby making belzutifan a uniquely optimal drug for targeting ccRCC. Belzutifan has demonstrated activity in clinical trials as a front- and later-line therapy, and in combination with tyrosine kinase inhibitors. It has been largely well tolerated, although anemia represents a common on-target side effect and, along with hypoxia, requires monitoring during treatment. Ongoing phase III trials are investigating belzutifan in combination regimens in the relapsed/refractory, front-line, and adjuvant settings. Future studies will focus on identifying predictive biomarkers and resistance pathways.

Targeting HIF-2α: the role of belzutifan in clear cell renal carcinoma management

INTRODUCTION

Belzutifan is a first-in-class hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor. It targets the von Hippel-Lindau protein (pVHL)-HIF-vascular endothelial growth factor (VEGF) pathway, which is crucial in cellular responses to hypoxia. By inhibiting HIF-2α, belzutifan disrupts the transcription of genes involved in tumor growth and angiogenesis.

AREAS COVERED

In this review, we describe the pVHL-HIF-VEGF pathway and how it led to the development of HIF inhibitors, including belzutifan. A search was conducted for trials involving Belzutifan, including phase I-III trials. We describe the relevant toxicity, with emphasis on hypoxia and anemia.

EXPERT OPINION

Belzutifan is a relatively safe drug, with manageable adverse events, including anemia and hypoxia as on-target toxicity. Ongoing trials are studying its benefit in overall survival for RCC in first-line treatment and its potential in other malignancies. The LITESPARK-005 trial reported the benefit of belzutifan in progression-free survival (PFS) compared to everolimus in later lines of treatment, with improvement in quality-of-life outcomes. Given its different mechanism of action to currently available treatments, belzutifan is expected to play a prominent role in the treatment of clear cell renal carcinoma and other cancers.

Belzutifan plus cabozantinib as first-line treatment for patients with advanced clear-cell renal cell carcinoma (LITESPARK-003): an open-label, single-arm, phase 2 study

BACKGROUND

Belzutifan, a first-in-class HIF-2α inhibitor, has shown antitumour activity as monotherapy and in combination with cabozantinib in patients with previously treated advanced kidney cancer. The phase 2 LITESPARK-003 study was designed to determine the antitumour activity and safety of belzutifan in combination with cabozantinib in patients with advanced clear-cell renal cell carcinoma that was previously untreated (cohort 1) or previously treated with immunotherapy (cohort 2). Here, we report results from cohort 1 of this clinical trial.

METHODS

LITESPARK-003 is an open-label, single-arm, phase 2 study at ten hospitals and cancer centres in the USA. In cohort 1, eligible patients were at least 18 years of age, had an Eastern Cooperative Oncology Group performance status of 0 or 1, and had received no previous systemic therapy for locally advanced or metastatic renal cell carcinoma. Patients received belzutifan 120 mg orally once daily and cabozantinib 60 mg orally once daily until unacceptable adverse events, disease progression, or patient withdrawal. The primary endpoint was investigator-assessed confirmed objective response according to Response Evaluation Criteria in Solid Tumors version 1.1. Antitumour activity and safety were assessed in all patients who received at least one dose of study treatment. This trial is registered with ClinicalTrials.gov, NCT03634540, and is ongoing.

FINDINGS

Between Sept 27, 2018, and Jan 10, 2023, we screened 138 patients for eligibility, and 50 (36%) were enrolled and assigned to cohort 1. The median age was 64 years (IQR 57-72). 40 (80%) of 50 patients were male and ten (20%) were female. 48 (96%) patients were White, one (2%) patient was Black or African American, and one (2%) was of a race in the other category. As of the data cutoff (May 15, 2023), median follow-up was 24·3 months (IQR 13·9-32·0). 35 (70%, 95% CI 55-82) of 50 patients had a confirmed objective response, including four (8%) who had a complete response and 31 (62%) who had a partial response. The most frequent grade 3-4 treatment-related adverse events were hypertension (six [12%] patients), anaemia (five [10%] patients), and fatigue (four [8%] patients). Seven (14%) of 50 patients had serious treatment-related adverse events. No treatment-related deaths occurred.

INTERPRETATION

Belzutifan plus cabozantinib has promising antitumour activity in treatment-naive patients with advanced clear-cell renal cell carcinoma and further investigation of an HIF-2α inhibitor in combination with a multitargeted tyrosine kinase inhibitor as a treatment option in this population is warranted.

FUNDING

Merck Sharp & Dohme LLC, a subsidiary of Merck & Co, Inc, Rahway, NJ, USA, and the National Cancer Institute.

The efficacy and safety of belzutifan inhibitor in patients with advanced or metastatic clear cell renal cell carcinoma: a meta-analysis

BACKGROUND

The belzutifan is a hypoxia inducible factor-2 alpha (HIF-2α) inhibitor for the treatment of advanced or metastatic clear cell renal cell carcinoma (mccRCC) and has exhibited good safety and efficacy in clinical trials. We conducted a meta-analysis of relevant studies to further clarify the efficacy and safety of belzutifan for the treatment of mccRCC.

METHODS

Multiple databases and abstracts from major scientific meetings were systematically reviewed for eligible articles published before June 1, 2024. The following outcomes were analyzed: objective response rate (ORR), disease control rate (DCR), median duration of response (mDOR), median progression-free survival (mPFS), median overall survival (mOS), and treatment-related adverse events (TRAes). 426 records were reviewed, and data were extracted by at least two individuals.

RESULTS

Seven studies involving 715 patients were included in this meta-analysis. The pooled ORR was 34% (95% confidence interval [CI]: 23-46%), the DCR was 79% (95% CI: 66-90%), the mDOR was 21.8 months (95% CI: 14.82-28.78), and the mPFS time was 8.8 months (95% CI: 6.15-11.44). The pooled incidence of grade 3-5 TRAes was 46%, and the most common TRAe was anemia. Further subgroup analysis revealed that, compared with belzutifan monotherapy, the combination of belzutifan with tyrosine kinase inhibitors (TKIs) as second- or later-line therapy was associated with a statistically significant increase in the ORR. Toxicity was also greater with combined inhibition therapy.

CONCLUSIONS

Our meta-analysis revealed moderate antitumor activity and a manageable safety profile of the inhibitor belzutifan in patients with mccRCC.

Cartilage Homeostasis under Physioxia

Articular cartilage receives nutrients and oxygen from the synovial fluid to maintain homeostasis. However, compared to tissues with abundant blood flow, articular cartilage is exposed to a hypoxic environment (i.e., physioxia) and has an enhanced hypoxic stress response. Hypoxia-inducible factors (HIFs) play a pivotal role in this physioxic environment. In normoxic conditions, HIFs are downregulated, whereas in physioxic conditions, they are upregulated. The HIF-α family comprises three members: HIF-1α, HIF-2α, and HIF-3α. Each member has a distinct function in articular cartilage. In osteoarthritis, which is primarily caused by degeneration of articular cartilage, HIF-1α is upregulated in chondrocytes and is believed to protect articular cartilage by acting anabolically on it. Conversely, in contrast to HIF-1α, HIF-2α exerts a catabolic influence on articular cartilage. It may therefore be possible to develop a new treatment for OA by controlling the expression of HIF-1α and HIF-2α with drugs or by altering the oxygen environment in the joints.

Rationale for immune checkpoint inhibitors plus targeted therapy for advanced renal cell carcinoma

Renal cell carcinoma (RCC) is a frequent urological malignancy characterized by a high rate of metastasis and lethality. The treatment strategy for advanced RCC has moved through multiple iterations over the past three decades. Initially, cytokine treatment was the only systemic treatment option for patients with RCC. With the development of medicine, antiangiogenic agents targeting vascular endothelial growth factor and mammalian target of rapamycin and immunotherapy, immune checkpoint inhibitors (ICIs) have emerged and received several achievements in the therapeutics of advanced RCC. However, ICIs have still not brought completely satisfactory results due to drug resistance and undesirable side effects. For the past years, the interests form researchers have been attracted by the combination of ICIs and targeted therapy for advanced RCC and the angiogenesis and immunogenic tumor microenvironmental variations in RCC. Therefore, we emphasize the potential principle and the clinical progress of ICIs combined with targeted treatment of advanced RCC, and summarize the future direction.

Belzutifan, HIF-2α Inhibitor, and Clear Cell Renal Cell Carcinoma With Somatic Von-Hippel-Lindau Loss-of-Function Mutation

The Von-Hippel-Lindau (VHL) gene, acting as a tumor suppressor, plays a crucial role in the tumorigenesis of clear cell renal cell carcinoma (ccRCC). Approximately 90% of individuals with advanced ccRCC exhibit somatic mutations in the VHL gene. Belzutifan, orally administered small-molecule inhibitor of hypoxia-induced factor-2α, has demonstrated promising efficacy in solid tumors associated with germline loss-of-function mutations in VHL, including ccRCC. However, its impact on cases with somatic or sporadic VHL mutations remains unclear. Here, we present 2 cases where belzutifan monotherapy was employed in patients with advanced ccRCC and somatic loss-of-function mutations in VHL. Both patients exhibited a swift and sustained response, underscoring the potential role of belzutifan as a viable option in second or subsequent lines of therapy for individuals with somatic VHL mutations. Despite both patients experiencing a pulmonary crisis with respiratory compromise, their rapid response to belzutifan further emphasizes its potential utility in cases involving pulmonary or visceral crises. This report contributes valuable insights into the treatment landscape for advanced ccRCC with somatic VHL mutations.