HIF-2α Inhibitor Research Articles

Belzutifan treatment for von Hippel-Lindau (VHL) disease–associated central nervous system (CNS) hemangioblastomas (HBs) in the phase 2 LITESPARK-004 study.

2008 Background: Patients (pts) with VHL disease are at risk for developing multiorgan tumors and cysts, including CNS HBs. The first-in-class hypoxia-inducible factor 2α (HIF-2α) inhibitor belzutifan showed clinically meaningful antitumor activity in VHL disease–associated renal cell carcinoma (RCC) and other neoplasms in the ongoing, single-arm, phase 2 LITESPARK-004 study (NCT03401788). We present updated results for the subgroup of pts with CNS HBs. Methods: Adults with a VHL disease diagnosis based on germline VHL alteration, ≥1 measurable RCC tumor, no RCC tumor > 3 cm or other VHL tumor requiring immediate surgical intervention, no evidence of metastatic disease, no prior systemic anticancer treatment, and an ECOG PS score of 0 or 1 received belzutifan 120 mg orally once daily. End points evaluated in pts with CNS HBs included objective response rate (ORR), duration of response (DOR), time to response (TTR), and progression-free survival (PFS) per RECIST v1.1 by an independent review committee; linear growth rate (LGR); and safety. CNS HBs were assessed using 2 methodologies: 1) with measurable (≥1 cm) and/or nonmeasurable disease at baseline and with associated cysts, if present; and 2) with measurable disease at baseline, excluding associated cysts, if present, from the lesion measurement. Results: Of 61 enrolled pts, 50 (82%) had ≥1 CNS HB evaluable at baseline, and 22 (59%) pts had undergone ≥1 CNS-related surgery within 4 years prior to starting belzutifan treatment. As of the April 1, 2022 data cutoff date, median study follow-up for pts with CNS HBs was 38.0 mo (range, 36.1-46.1). ORR was 44% (n = 22; 95% CI, 30-59; 4 CRs, 18 PRs), and DCR was 90% (n = 45; 95% CI, 78-97). Median TTR was 5.4 mo (range, 2.3-33.1), and median DOR was not reached (NR; range, 3.7+ to 38.7+ mo). Median PFS was NR (95% CI, 38 mo to NR). After initiating belzutifan, median LGR for all evaluable pts was –1.6 mm/year (range, –7.0 to 3.1). Of all pts, 25/50 (50%) had ≥1 measurable CNS HBs, excluding any associated cysts. For these pts, ORR was 76% (95% CI, 55-91; 1 CR, 18 PRs), and DCR was 96% (n = 24; 95% CI, 80-100). Median TTR was 3.1 mo (range, 2.5-27.8), and median DOR was NR (range, 3.7+ to 38.7+ mo). Median PFS was NR (95% CI, 36 mo to NR). After initiating belzutifan, median LGR was –1.1 mm/year (range, –3.9 to –0.1). Of all pts, 1/50 (2%) underwent a CNS-related surgery after starting belzutifan. Two (3%) pts discontinued treatment due to treatment-related adverse events. Conclusions: With more than 3 years of treatment with belzutifan, consistent and durable antitumor activity was observed in pts with CNS HBs, which is consistent with findings in other VHL disease–associated neoplasms. Using different methodologies of assessing tumors, our data demonstrated that belzutifan induced the shrinkage of VHL disease–related CNS HBs with or without the presence of associated cysts. Clinical trial information: NCT03401788 .

Real-world outcomes and safety in patients with VHL associated tumors receiving belzutifan.

10515 Background: Belzutifan, a small molecule HIF-2α inhibitor was FDA approved for the treatment of VHL-associated renal cell carcinoma (RCC), CNS hemangioblastomas and pancreatic NET (pNET). The approval was based on the results from the phase 2, open-label, single-group trial, enrolling 61 patients at approximately 12 study sites (Srinivasan, 2021). Objective responses were seen in 49% patients with VHL associated RCC, 63% patients with VHL-associated CNS hemangioblastomas, and 83% of patients with VHL-associated pNET. Common adverse events included anemia, fatigue, renal dysfunction, nausea, and elevated glucose levels. There is currently very limited data on real-world outcomes using belzutifan in VHL patients. Methods: After obtaining IRB approval, we retrospectively evaluated the efficacy and safety of Belzutifan for patients with VHL disease and renal cell cancer and/or VHL-associated tumors who received Belzutifan between August 2021 and January 2023 at KU Cancer center. Results: A total of 16 patients are started on Belzutifan treatment. The baseline characteristics include median age of 45 years, including 8 (50%) females and 8 (50%) males. Patients with VHL-associated RCCs were seen in 15 patients (n = 15), VHL-associated pNET (n = 13), and CNS hemangioblastomas (n = 13). Patients were started on belzutifan 120mg daily. The patients underwent bloodwork and clinic follow-up every 6-8 weeks, and response assessment was done in 11/15 patients who had follow-up scans at 6-month intervals. Objective Response to Belzutifan in any of these VHL-associated tumors was seen in 9 of 11 patients (81%), and 1/11(9%) had progressive disease (PD). Objective response in patients with VHL-associated RCC was observed in 8/11 (72%) patients and 2/11 (18%) with partial response (PR), and 6/11 (54%) with stable disease (SD). Responses observed in patients with pancreatic lesions were 1/11 patients (9%) with CR, 1/11 (9%) with PR, and 5/11 (45%) with SD. Patients with CNS hemangioblastomas 4/9 (44%) had SD. Safety was assessed in all the patients. The predominant side effect was anemia 12/16 (75%) and fatigue 11/16 (68%). Other side effects reported are fogginess 4/16 (25%), nausea 2/16 (12.5%), dizziness 2/16 (12.5%), and shortness of breath 2/16 (12.5%). Dose reduction to 80mg was needed in 2/16 (12.5%) patients due to moderate fatigue, hypoxia in one, and dysgeusia, respectively. Conclusions: Our real-world outcomes analysis of patients with VHL-associated tumors who are treated with Belzutifan shows an improved objective response when compared to the initial clinical trials, which is promising for patients. The analysis based on our real-world data shows the superior objective response in VHL-associated RCCs with Belzutifan, with a manageable safety profile. These findings reinforce Belzutifan as an effective treatment option for this patient population but warrant confirmation in a larger sample.

Belzutifan plus lenvatinib for patients (pts) with advanced clear cell renal cell carcinoma (ccRCC) after progression on a PD-1/L1 and VEGF inhibitor: Preliminary results of arm B5 of the phase 1/2 KEYMAKER-U03B study.

4553 Background: The oral HIF-2α inhibitor belzutifan demonstrated antitumor activity with manageable safety as monotherapy in pts with heavily pretreated ccRCC and in combination with a VEGF-TKI in pts who previously received a PD-1/L1 inhibitor. KEYMAKER-U03B (NCT04626518) is phase 1/2, multicenter, multi-arm, open-label, adaptive umbrella study. We present preliminary results from arm B5 for belzutifan + lenvatinib. Methods: In all arms, adults with histologically confirmed ccRCC, KPS ≥70%, and disease progression on or after PD-1/L1 inhibitor and VEGF-TKI treatment (in sequence or in combination) were enrolled. In arm B5, pts received belzutifan 120 mg PO QD + lenvatinib 20 mg PO QD. The study comprised a safety lead-in phase to establish the recommended phase 2 dose (RP2D), followed by an efficacy phase. Primary end point for the safety lead-in phase was safety and tolerability to establish RP2D; co-primary end points of the efficacy phase were safety and ORR per RECIST v1.1 by blinded independent central review (BICR). Secondary end points include clinical benefit rate (CBR; CR + PR + SD ≥6 mo), DOR and PFS per RECIST v1.1 by BICR. Response will be presented in pts who had an opportunity to receive ≥2 postbaseline scans due to ongoing enrollment. PFS was evaluated in all enrolled pts and safety in all treated pts. End points will be evaluated in each arm separately; no comparisons will be made across arms. Results: As of September 29, 2022, 32 pts were enrolled and 30 received treatment. Median age was 60.5 y, 78% were male and 78% had intermediate/poor IMDC risk. 23 pts were on treatment at data cutoff date. Median follow up was 6.9 mo (range: 0.1-18.2). Safety of belzutifan 120 mg + lenvatinib 20 mg was manageable. Of 10 evaluable pts in the safety lead-in phase, only 1 experienced a dose-limiting toxicity (grade 1 dyspnea). Among pts who had opportunity for ≥2 postbaseline scans (n = 24), ORR was 50% (95% CI, 29-71; all PRs); CBR was 54% (95% CI, 33-74). Median DOR was not reached (NR; range: 1.4+ to 14.0+ mo); 74% of responders remained in response for ≥12 mo by KM estimation. For all enrolled pts, median PFS was 11.2 mo (95% CI, 4-NR); 6-mo rate was 55%. In the safety analysis, 28 pts (93%) experienced a treatment-related AE (TRAE), most commonly (≥40%) anemia (43%), fatigue (43%), and hypertension (43%). Grade 3-4 TRAEs occurred in 15 pts (50%); most commonly hypertension (27%) and anemia (17%). 1 pt experienced grade 2 hypoxia. No pt died due to a TRAE. Conclusions: Preliminary data from the belzutifan + lenvatinib combination exhibited promising antitumor activity in pts with ccRCC that progressed on PD-1/L1 inhibitors and VEGF-TKIs. Safety findings were consistent with individual profiles of each agent. The combination is being further evaluated in the phase 3 LITESPARK-011 study. Clinical trial information: NCT04626518 .

ARC-20: A phase 1 dose-escalation and dose-expansion study to investigate the safety, tolerability, and pharmacology of HIF-2α inhibitor AB521 monotherapy in patients with clear cell renal cell carcinoma and other solid tumors.

TPS4602 Background: Renal cell carcinoma (RCC) is one of the 10 most common neoplasms in the United States. Patients with clear cell RCC (ccRCC) commonly have inactivation of the von Hippel-Lindau tumor suppressor protein, resulting in accumulation of hypoxia-inducible factor alpha (HIFα) subunits (especially HIF-2α) and leading to tumor growth. AB521, an orally bioavailable small molecule inhibitor of HIF-2α, potently inhibits transcription of HIF-2α-dependent genes in cell lines and preclinical species. Single doses of AB521 (3 mg, 10 mg, 30 mg, and 100 mg) and multiple ascending doses of AB521 (15 mg, 30 mg, and 50 mg) have been previously studied in healthy volunteers. ARC-20 is a first-in-patient study to investigate the safety, tolerability, and pharmacology of AB521 monotherapy in patients with solid tumors and evaluate the clinical activity of AB521 in previously treated patients with ccRCC. Methods: ARC-20 (NCT05536141) is a phase 1, multicenter, open-label study. Eligible patients are adults with solid tumors with ≥1 measurable lesion(s) per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 and an Eastern Cooperative Oncology Group performance status of 0 or 1. ARC-20 has 2 stages, dose escalation and dose expansion. The dose escalation stage uses a standard 3+3 design and includes patients with pathologically confirmed solid tumors and no other available treatment options. Patients will be sequentially assigned to 1 of 4 cohorts evaluating doses of AB521 ranging from 20 to 200 mg/day. Intermediate dose cohorts may be evaluated based on emergent safety or pharmacologic data. The dose expansion stage will evaluate approximately 30 patients with histologically confirmed ccRCC who have received previous treatment for metastasis with an anti-programmed cell death protein 1 (anti-PD-1) therapy and a vascular endothelial growth factor (VEGF)-targeting tyrosine kinase inhibitor (TKI). Patients previously treated with a HIF-2α-targeting therapy are not eligible for dose expansion. Results from the dose-escalation stage will inform the dose and schedule used during dose expansion. Primary endpoints are the incidence of dose-limiting toxicity and adverse events. Secondary endpoints include objective response rate, AB521 plasma concentration, and AB521 pharmacokinetics. Exploratory endpoints include changes in expression of erythropoietin and other HIF-2α driven biomarkers in blood and tumor tissues, along with progression-free survival for ccRCC patients during dose expansion. Clinical trial information: NCT05536141 .

Belzutifan plus cabozantinib for patients with advanced clear cell renal cell carcinoma previously treated with immunotherapy: an open-label, single-arm, phase 2 study.

Few treatment options are available for patients with advanced renal cell carcinoma who have received previous anti-PD-1-based or anti-PD-L1-based immunotherapy. Combining belzutifan, an HIF-2α inhibitor, with cabozantinib, a multitargeted tyrosine-kinase inhibitor of VEGFR, c-MET, and AXL, might provide more antitumoural effects than either agent alone. We aimed to investigate the antitumour activity and safety of belzutifan plus cabozantinib in patients with advanced clear cell renal cell carcinoma that was previously treated with immunotherapy. This open-label, single-arm, phase 2 study was conducted at ten hospitals and cancer centres in the USA. Patients were enrolled into two cohorts. Patients in cohort 1 had treatment-naive disease (results will be reported separately). In cohort 2, eligible patients were aged 18 years or older with locally advanced or metastatic clear cell renal cell carcinoma, measurable disease according to Response Evaluation Criteria in Solid Tumours version 1.1, an Eastern Cooperative Oncology Group performance status score of 0 or 1, and had previously received immunotherapy and up to two systemic treatment regimens. Patients were given belzutifan 120 mg orally once daily and cabozantinib 60 mg orally once daily until disease progression, unacceptable toxicity, or patient withdrawal. The primary endpoint was confirmed objective response assessed by the investigator. 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. Between Sept 27, 2018, and July 14, 2020, 117 patients were screened for eligibility, 52 (44%) of whom were enrolled in cohort 2 and received at least one dose of study treatment. Median age was 63·0 years (IQR 57·5-68·5), 38 (73%) of 52 patients were male, 14 (27%) were female, 48 (92%) were White, two (4%) were Black or African American, and two were Asian (4%). As of data cutoff (Feb 1, 2022), median follow-up was 24·6 months (IQR 22·1-32·2). 16 (30·8% [95% CI 18·7-45·1]) of 52 patients had a confirmed objective response, including one (2%) who had a complete response and 15 (29%) who had partial responses. The most common grade 3-4 treatment-related adverse event was hypertension (14 [27%] of 52 patients). Serious treatment-related adverse events occurred in 15 (29%) patients. One death was considered treatment related by the investigator (respiratory failure). Belzutifan plus cabozantinib has promising antitumour activity in patients with pretreated clear cell renal cell carcinoma and our findings provide rationale for further randomised trials with belzutifan in combination with a VEGFR tyrosine-kinase inhibitor. Merck Sharp & Dohme (a subsidiary of Merck & Co) and the National Cancer Institute.

Discovery of novel direct small-molecule inhibitors targeting HIF-2α using structure-based virtual screening, molecular dynamics simulation, and MM-GBSA calculations.

Hypoxia-inducible factors (HIFs) are the main regulatory factors implicated in the adaptation of cancer cells to hypoxic stress, which has provoked much interest as an attractive target for the design of promising chemotherapeutic agents. Since indirect HIF inhibitors (HIFIs) lead to the occurrence of various side effects, the need of the hour is to develop direct HIFIs, physically interacting with important functional domains within the HIF protein structure. Accordingly, in the present study, it was attempted to develop an exhaustive structure-based virtual screening (VS) process coupled with molecular docking, molecular dynamic (MD) simulation, and MM-GBSA calculations for the identification of novel direct inhibitors against the HIF-2α subunit. For this purpose, a focused library of over 200,000 compounds from the NCI database was used for VS against the PAS-B domain of the target protein, HIF-2α. This domain was suggested to be a possible ligand-binding site, which is characterized by a large internal hydrophobic cavity, unique to the HIF-2α subunit. The top-ranked compounds, NSC106416, NSC217021, NSC217026, NSC215639, and NSC277811 with the best docking scores were taken up for the subsequent in silico ADME properties and PAINS filtration. The selected drug-like hits were employed for carrying out MD simulation which was followed by MM-GBSA calculations to retrieve the candidates showing the highest in silico binding affinity towards the PAS-B domain of HIF-2α. The analysis of results indicated that all molecules, except the NSC277811, fulfilled necessary drug-likeness properties. Four selected drug-like candidates, NSC106416, NSC217021, NSC217026, and NSC215639 were found to expose the stability profiles within the cavity located inside the PAS-B domain of HIF-2α over simulation time. Finally, the results of the MM-GBSA rescoring method were indicative of the highest binding affinity of NSC217026 for the binding site of the HIF-2α PAS-B domain among selected final hits. Consequently, the hit NSC217026 could serve as a promising scaffold for further optimization toward the design of direct HIF-2α inhibitors for cancer therapy.

Abstract CT120: The randomized phase 1/2 LITESPARK-024 study of belzutifan with or without palbociclib in patients with advanced renal cell carcinoma (RCC)

Abstract Background: First-line treatment with immunotherapy alone or in combination with antiangiogenic agents is a standard of care for advanced RCC. Many patients (pts) develop resistance to first-line treatment and effective second-line and beyond options are needed. The von Hippel-Lindau (VHL) gene is inactivated in approximately 90% of RCC cases, which results in the constitutive activation of hypoxia-inducible factor 2α (HIF-2α), a key oncogenic driver in RCC. The first-in-class HIF-2α inhibitor belzutifan has demonstrated promising antitumor activity with manageable safety in previously treated pts with advanced RCC. The cyclin-dependent kinase (CDK) pathway has also been implicated in RCC and is associated with poor clinical outcomes. In RCC cell lines, the CDK 4/6 inhibitor palbociclib inhibited cell growth. The addition of CDK 4/6 inhibition had synergistic antiproliferative effects with HIF-2α inhibition in HIF-2α-dependent VHL -/- RCC cell lines. Palbociclib could therefore potentially enhance the efficacy of belzutifan as combination therapy for previously treated pts with advanced RCC. Methods: The two-part, open-label, multicenter, phase 1/2 randomized LITESPARK-024 study (NCT05468697) is intended to establish the recommended phase 2 dose (RP2D) of belzutifan + palbociclib in combination with a modified toxicity probability interval design (Part 1), followed by a direct comparison of belzutifan monotherapy to the combination with respect to safety and efficacy in pts with advanced RCC (Part 2). Pts with histologically confirmed unresectable stage IV RCC with a clear cell component, whose disease progressed on or after having received at least 2 systemic treatments (both an anti-PD-1/PD-L1 monoclonal antibody and a VEGF receptor-targeted tyrosine kinase inhibitor, in sequence or in combination), have measurable disease per RECIST v1.1 by blinded independent central review, and have KPS score of ≥70% will be enrolled. Up to 30 pts will be enrolled into 3 dose groups in Part 1 and will receive belzutifan 120 mg once daily + palbociclib (75, 100, or 125 mg) daily for 21 consecutive days followed by 7 days off. In part 2, approximately 150 pts will be randomly assigned 2:1 to receive belzutifan 120 mg once daily + palbociclib RP2D (21 consecutive days/7 days off) or belzutifan 120 mg once daily. Pts will be stratified by IMDC risk (0 vs 1-2 vs 3-6) and sarcomatoid histology (yes vs no) at randomization in part 2. The primary end point for part 1 is to assess dose-limiting toxicities and adverse events to determine the RP2D of belzutifan + palbociclib. The primary end point for part 2 is ORR per RECIST v1.1 by investigator assessment. Secondary end points for part 2 are CBR, DOR, PFS, OS, and safety and tolerability. This abstract was accepted and previously presented at the 2023 ASCO Genitourinary Cancers Symposium. All rights reserved. Citation Format: David F. McDermott, Avivit Peer, Neeraj Agarwal, Michael B. Atkins, Jerry Cornell, Rodolfo F. Perini, Kenneth F. Grossmann, Howard Gurney. The randomized phase 1/2 LITESPARK-024 study of belzutifan with or without palbociclib in patients with advanced renal cell carcinoma (RCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT120.

Abstract 494: BPI-452080: A potent and selective HIF-2α inhibitor for the treatment of clear cell renal cell carcinoma, von Hippel-Lindau disease, and other solid tumors

Abstract The most observed alteration in clear cell renal cell carcinoma (ccRCC) is the inactivation of the tumor suppressor von Hippel-Lindau (VHL) E3 ligase due to genetic predisposition, somatic mutations, or methylation. Loss of VHL can lead to hypoxia-inducible factor 2α (HIF-2α) accumulation and elevated expression of HIF target genes, such as VEGFA, many of which facilitate angiogenesis, proliferation, and metastasis of ccRCC. Therefore, inhibiting HIF-2α has become a new strategy for the treatment of ccRCC. Here, we present the discovery of BPI-452080, a selective small molecule HIF-2α inhibitor. In VHL defective ccRCC cell lines, BPI-452080 potently and selectively blocked the heterodimerization of HIF-2α with HIF-1β, but not that of HIF-1α with HIF-1β. It inhibited the downstream hypoxia-responsive gene transcription and VEGFA protein secretion. In multiple xenograft mouse models, oral administration of BPI-452080 significantly inhibited tumor growth in a dose-dependent manner. BPI-452080 demonstrated good PK/PD correlation in the 786-O xenograft model after a single dosing, as shown by a concentration-dependent inhibition of VEGFA secretion in plasma and a reduction of the mRNA levels of VEGFA, CXCR4, CCND1, and GLUT1 genes in tumor tissue. Moreover, BPI-452080 exhibited good bioavailability in multiple pre-clinical species, favorable ADME properties, and good tolerance in toxicology studies. In conclusion, BPI-452080 is a potent, selective, and orally bioavailable HIF-2α inhibitor which presents a novel therapeutic option for ccRCC, von Hippel-Lindau disease, and other solid tumors. BPI-452080 is planned to enter Phase I clinical trial in China in early 2023. Citation Format: Pingping Wang, Rongwen Yang, Yun Sun, Xuepeng Ju, Jiayu Zhao, Yanju Liu, Xiaoyun Liu, Zhengyao Zou, Jialin Ren, Min Wang, Haibo Chen, Xuegang Yi, Jian Zhang, Teng Ma, Gaoliang Cheng, Lijia Liu, Jing Guo, Xiangyong Liu, Hong Lan, Lieming Ding, Jiabing Wang. BPI-452080: A potent and selective HIF-2α inhibitor for the treatment of clear cell renal cell carcinoma, von Hippel-Lindau disease, and other solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 494.

Personalized Systemic Therapies in Hereditary Cancer Syndromes.

Hereditary cancer syndromes are inherited disorders caused by germline pathogenic variants (PVs) that lead to an increased risk of developing certain types of cancer, frequently at an earlier age than in the rest of the population. The germline PVs promote cancer development, growth and survival, and may represent an ideal target for the personalized treatment of hereditary tumors. PARP inhibitors for the treatment of BRCA and PALB2-associated tumors, immune checkpoint inhibitors for tumors associated with the Lynch Syndrome, HIF-2α inhibitor in the VHL-related cancers and, finally, selective RET inhibitors for the treatment of MEN2-associated medullary thyroid cancer are the most successful examples of how a germline PVs can be exploited to develop effective personalized therapies and improve the outcome of these patients. The present review aims to describe and discuss the personalized systemic therapies for inherited cancer syndromes that have been developed and investigated in clinical trials in recent decades.

Specific HIF-2α (Hypoxia-Inducible Factor-2) Inhibitor PT2385 Mitigates Placental Dysfunction In Vitro and in a Rat Model of Preeclampsia (RUPP).

Preeclampsia is one of the leading causes of maternal mortality worldwide and is strongly associated with long-term morbidity in mothers and newborns. Referred to as one of the deep placentation disorders, insufficient remodeling of the spiral arteries during the first trimester remains a major cause of placental dysfunction. Persisting pulsatile uterine blood flow causes abnormal ischemia/reoxygenation phenomenon in the placenta and stabilizes the HIF-2α (hypoxia-inducible factor-2α) in the cytotrophoblasts. HIF-2α signaling impairs trophoblast differentiation and increases sFLT-1 (soluble fms-like tyrosine kinase-1) secretion, which reduces fetal growth and causes maternal symptoms. This study aims to evaluate the benefits of using PT2385-an oral specific HIF-2α inhibitor-to treat severe placental dysfunction. To evaluate its therapeutic potential, PT2385 was first studied in primary human cytotrophoblasts isolated from term placenta and exposed to 2.5% O2 to stabilize HIF-2α. Viability and luciferase assays, RNA sequencing, and immunostaining were used to analyze differentiation and angiogenic factor balance. The ability of PT2385 to mitigate maternal manifestations of preeclampsia was studied in the selective reduced uterine perfusion pressure model performed in Sprague-Dawley rats. In vitro, RNA sequencing analysis and conventional techniques showed that treated cytotrophoblast displayed an enhanced differentiation into syncytiotrophoblasts and normalized angiogenic factor secretion compared with vehicle-treated cells. In the selective reduced uterine perfusion pressure model, PT2385 efficiently decreased sFLT-1 production, thus preventing the onset of hypertension and proteinuria in pregnant dams. These results highlight HIF-2α as a new player in our understanding of placental dysfunction and support the use of PT2385 to treat severe preeclampsia in humans.

Phase 3 LITESPARK-022: Pembrolizumab (pembro) plus hypoxia-inducible factor 2α (HIF-2α) inhibitor belzutifan as adjuvant treatment for clear cell renal cell carcinoma (ccRCC).

TPS748 Background: Treatment with the PD-1 inhibitor pembro produced significant improvement in disease-free survival after surgery for patients (pts) with ccRCC in the phase 3 KEYNOTE-564 trial. Based on these results, pembro was approved by the US Food and Drug Administration and the European Medicines Agency for adjuvant treatment of pts with RCC at increased risk of recurrence following nephrectomy or following nephrectomy and resection of metastatic lesions. Despite advances in the treatment landscape for RCC, more effective adjuvant treatment strategies are needed for pts at risk of recurrence after surgery. HIF-2α is an established oncogenic driver in ccRCC, and promising antitumor activity in advanced ccRCC and von Hippel-Lindau disease–associated RCC has been demonstrated with the HIF-2α inhibitor belzutifan. The multicenter, double-blind, randomized, phase 3 LITESPARK-022 study (NCT05239728) will evaluate the efficacy and safety of pembro plus belzutifan compared with placebo plus pembro as adjuvant treatment following nephrectomy in pts with ccRCC. Methods: Key eligibility criteria include adults with histologically or cytologically confirmed intermediate-high risk, high risk, or M1 with no evidence of disease (NED) RCC with a clear cell component; pts with no prior systemic therapy, nephrectomy, and/or metastasectomy ≤12 weeks before randomization; and pts who are tumor free per computed tomography/magnetic resonance imaging. Approximately 1600 pts will be randomly assigned to receive belzutifan 120 mg orally once daily plus pembro 400 mg intravenously (IV) every 6 weeks (Q6W) for ≤9 administrations (~54 weeks) or oral placebo plus pembro 400 mg IV Q6W for ≤9 administrations (~54 weeks) or until verified disease recurrence by blinded independent central review, start of new anticancer treatment, unacceptable toxicity, or decision to withdraw. Stratification factors are tumor grade (1 or 2 vs 3 or 4) and risk type (intermediate-high risk versus high risk versus M1 NED). Pts will be radiologically evaluated Q12W from randomization through year 2, Q16W in years 3 to 5, and Q24W in years 6 and beyond. Adverse events will be monitored throughout the study and for 30 days following cessation of study treatment (90 days for serious adverse events). The primary end point is disease-free survival. Secondary end points include overall survival, safety, disease recurrence–specific survival, and patient-reported outcomes. Recruitment is underway in Asia, Australia, Europe, North America, and South America. © 2022 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2022 ASCO Annual Meeting. All rights reserved. Clinical trial information: NCT05239728 .

LITESPARK-024: A randomized phase 1/2 study of belzutifan with or without palbociclib in patients with advanced renal cell carcinoma.

TPS747 Background: The combination of immunotherapy with antiangiogenic agents is a well-established first-line treatment option for patients (pts) with advanced renal cell carcinoma (RCC), but many pts develop resistance, and effective second- or subsequent-line options are needed. The von Hippel-Lindau ( VHL) gene is inactivated in approximately 90% of RCC cases, which results in the constitutive activation of hypoxia-inducible factor 2α (HIF-2α) signaling. HIF-2α is involved in angiogenesis, tumor growth, proliferation, and metastasis, and is a key oncogenic driver in RCC. The HIF-2α inhibitor belzutifan has demonstrated promising antitumor activity with manageable safety in pts with heavily pretreated RCC. The cyclin-dependent kinase (CDK) pathway is altered in several cancer types, including RCC, and is associated with poor clinical outcomes. The CDK 4/6 inhibitor palbociclib inhibited cell growth in RCC cell lines, and the antiproliferative effects of CDK 4/6 inhibition were synergistic with HIF-2α inhibition in HIF-2α–dependent VHL -/- clear cell RCC cell lines. We hypothesized palbociclib could potentially enhance the efficacy of belzutifan as combination therapy for previously treated pts with advanced RCC. Methods: LITESPARK-024 (NCT05468697) is an open-label, multicenter, phase 1/2 randomized study of belzutifan + palbociclib versus belzutifan monotherapy in pts with advanced RCC. Pts must have histologically confirmed unresectable stage IV RCC with a clear cell component, received at least 2 prior systemic regimens (both an anti–PD-1/PD-L1 monoclonal antibody and a VEGF receptor–targeted TKI, in sequence or in combination), have measurable disease per RECIST v1.1 by BICR, have KPS score of ≥70%, and have radiographic disease progression on or after the most recent regimen per investigator. Part 1 will evaluate the safety of belzutifan + palbociclib and determine the recommended phase 2 dose (RP2D) for the combination using a modified toxicity probability interval design. Part 2 will evaluate the safety and efficacy of belzutifan + palbociclib versus belzutifan alone. In part 1, ≤30 pts will be enrolled into 3 dose groups and receive belzutifan 120 mg once daily + palbociclib (75, 100, or 125 mg) daily for 21 consecutive days followed by 7 days off. In part 2, approximately 150 pts will be randomly assigned 2:1 to receive belzutifan 120 mg once daily + palbociclib RP2D (21 consecutive days/7 days off) or belzutifan 120 mg once daily. Pts will be stratified by IMDC risk (0 vs 1-2 vs 3-6) and sarcomatoid histology (yes vs no) at randomization in part 2. The primary end point for part 1 is to assess dose-limiting toxicities and adverse events to determine the RP2D of belzutifan + palbociclib. The primary end point for part 2 is ORR per RECIST v1.1 by investigator assessment. Secondary end points for part 2 are clinical benefit rate, DOR, PFS, OS, and safety and tolerability. Clinical trial information: NCT05468697 .

Development of drugs targeting hypoxia-inducible factor against tumor cells with VHL mutation: Story of 127 years.

Intratumoral hypoxia is associated with tumor progression and therapeutic resistance. The VHL tumor suppressor gene was identified in 1993, and later studies revealed that the gene product pVHL interacts with other proteins to form the VBC complex. The VBC complex functions as an E3 ubiquitin ligase and regulates the abundance of the α-subunit of the transcription factor hypoxia-inducible factor (HIF). Hypoxia-inducible factor regulates thousands of genes required for cells to adapt and survive in hypoxic conditions, and thus pVHL plays a major role in oxygen-sensing pathways. Patients with von Hippel-Lindau (VHL) disease, harboring a germline mutation of the VHL gene, develop renal cell carcinomas and a series of tumors showing hypervascular phenotypes. The extensive findings that have clarified the function of VHL have contributed to the development of novel first-in-human drugs, including belzutifan, a HIF-2α inhibitor. The 2019 Nobel Prize in Physiology or Medicine was awarded to Dr. William G. Kaelin Jr., Dr. Peter J. Ratcliffe, and Dr. Gregg L. Semenza as researchers contributing to clarifying the mechanism of the oxygen-sensing pathway of cells. The first report of VHL disease was in 1894, meaning the development of a specific drug for this disease took almost 125 years. In this article, we describe how researchers and clinician scientists successfully clarified the function of VHL and achieved a preclinical proof of concept to apply for clinical trials, key requirements for drug development.

Comprehensive in silico and functional studies for classification of EPAS1/HIF2A genetic variants identified in patients with erythrocytosis.

Gain-of-function mutations in the EPAS1/HIF2A gene have been identified in patients with hereditary erythrocytosis that can be associated with the development of paraganglioma, pheochromocytoma and somatostatinoma. In the present study, we describe a unique European collection of 41 patients and 28 relatives diagnosed with an erythrocytosis associated with a germline genetic variant in EPAS1. In addition we identified two infants with severe erythrocytosis associated with a mosaic mutation present in less than 2% of the blood, one of whom later developed a paraganglioma. The aim of this study was to determine the causal role of these genetic variants, to establish pathogenicity, and to identify potential candidates eligible for the new hypoxia-inducible factor-2 α (HIF-2α) inhibitor treatment. Pathogenicity was predicted with in silico tools and the impact of 13 HIF-2b variants has been studied by using canonical and real-time reporter luciferase assays. These functional assays consisted of a novel edited vector containing an expanded region of the erythropoietin promoter combined with distal regulatory elements which substantially enhanced the HIF-2α-dependent induction. Altogether, our studies allowed the classification of 11 mutations as pathogenic in 17 patients and 23 relatives. We described four new mutations (D525G, L526F, G527K, A530S) close to the key proline P531, which broadens the spectrum of mutations involved in erythrocytosis. Notably, we identified patients with only erythrocytosis associated with germline mutations A530S and Y532C previously identified at somatic state in tumors, thereby raising the complexity of the genotype/phenotype correlations. Altogether, this study allows accurate clinical follow-up of patients and opens the possibility of benefiting from HIF-2α inhibitor treatment, so far the only targeted treatment in hypoxia-related erythrocytosis disease.

Belzutifan (MK-6482): Biology and Clinical Development in Solid Tumors.

To review the biology, drug development, and clinical data regarding the efficacy and safety of belzutifan (MK-6482), a small molecule inhibitor of HIF-2α. Belzutifan, a second-generation HIF-2α inhibitor, was shown to provide clinically meaningful benefit in the treatment of VHL-associated tumors (including ccRCC, pancreatic lesions as well as neuroendocrine tumor, and CNS hemangioblastomas). The recommended dose of belzutifan is 120mg orally daily and half-life is 14h. In pretreated ccRCC, belzutifan achieved disease control rate of 80% in phase I trial. The most common side effects include anemia and hypoxia related symptoms. Investigation into the important role HIF-2α plays in the expression of genes associated with angiogenesis, erythropoiesis, carcinogenesis, and progression of tumors and the discovery of structural vulnerability within HIF-2α have resulted in the development of a new therapy that has demonstrated efficacy and safety in recent clinical trials. Further research is ongoing to optimize therapeutic benefits from this new exciting therapeutic modality and to improve the outcome of HIF-2α-driven tumors.

LITESPARK-011: belzutifan plus lenvatinib vs cabozantinib in advanced renal cell carcinoma after anti-PD-1/PD-L1 therapy.

The first-in-class, small molecule HIF-2αinhibitor, belzutifan, has demonstrated promising antitumor activity in previously treated patients with clear cell renal cell carcinoma (RCC). HIF-2α also regulates VEGF expression and is involved in resistance to anti-VEGF therapy. This study describes the rationale and design for a randomized, phase III study evaluating efficacy and safety of belzutifan plus the tyrosine kinase inhibitor (TKI) lenvatinib versus the TKI cabozantinib in patients with advanced RCC progressing after anti-PD-1/PD-L1 therapy in the first- or second-line setting or as adjuvant therapy. Considering the unmet need for effective and tolerable treatment of advanced RCC following immune checkpoint inhibitors, belzutifan plus lenvatinib may have a positive benefit/risk profile. Clinical Trial Registration: NCT04586231 (ClinicalTrials.gov).

The road to systemic therapy in von Hippel-Lindau (VHL) disease: Are we there yet?

Pathogenic germline mutations in VHL gene cause von Hippel-Lindau (VHL) disease, an autosomal dominant hereditary cancer syndrome associated with high penetrance of benign and malignant neoplasms, including clear cell renal cell carcinoma (ccRCC), central nervous system haemangioblastomas (CNS-HB), retinal angiomas, phaeochromocytomas and pancreatic neuroendocrine tumours (pNET). Management of VHL disease involves lifelong radiological and biochemical surveillance, often leading to repeat surgical intervention causing significant morbidity and mortality. Systemic therapy that prevents or reduces the need for surgical intervention could improve clinical outcomes and quality of life for affected individuals. Belzutifan is a second-generation small molecule hypoxia-inducible factor 2α (HIF-2α) inhibitor recently approved by US and UK regulators for the treatment of VHL (disease)-associated ccRCC, CNS-HB and pNET. While this is a welcome step forward, it is vital that we consider in what circumstances these drugs are recommended and how they fit into the overall management of VHL disease. In this personal view article, we reflect on the history of the use of systemic therapy in localised VHL disease and consider open questions relating to the use of HIF-2α inhibitors, including the need to involve medical oncologists in the multidisciplinary team moving forward. Indeed, VHL disease is the perfect paradigm for similar settings in the future.

CD70-Targeted Micelles Enhance HIF2α siRNA Delivery and Inhibit Oncogenic Functions in Patient-Derived Clear Cell Renal Carcinoma Cells.

The majority of clear cell renal cell carcinomas (ccRCCs) are characterized by mutations in the Von Hippel−Lindau (VHL) tumor suppressor gene, which leads to the stabilization and accumulation of the HIF2α transcription factor that upregulates key oncogenic pathways that promote glucose metabolism, cell cycle progression, angiogenesis, and cell migration. Although FDA-approved HIF2α inhibitors for treating VHL disease-related ccRCC are available, these therapies are associated with significant toxicities such as anemia and hypoxia. To improve ccRCC-specific drug delivery, peptide amphiphile micelles (PAMs) were synthesized incorporating peptides targeted to the CD70 marker expressed by ccRCs and anti-HIF2α siRNA, and the ability of HIF2α-CD27 PAMs to modulate HIF2α and its downstream targets was evaluated in human ccRCC patient-derived cells. Cell cultures were derived from eight human ccRCC tumors and the baseline mRNA expression of HIF2A and CD70, as well as the HIF2α target genes SLC2A1, CCND1, VEGFA, CXCR4, and CXCL12 were first determined. As expected, each gene was overexpressed by at least 63% of all samples compared to normal kidney proximal tubule cells. Upon incubation with HIF2α-CD27 PAMs, a 50% increase in ccRCC-binding was observed upon incorporation of a CD70-targeting peptide into the PAMs, and gel shift assays demonstrated the rapid release of siRNA (>80% in 1 h) under intracellular glutathione concentrations, which contributed to ~70% gene knockdown of HIF2α and its downstream genes. Further studies demonstrated that knockdown of the HIF2α target genes SLC2A1, CCND1, VEGFA, CXCR4, and CXCL12 led to inhibition of their oncogenic functions of glucose transport, cell proliferation, angiogenic factor release, and cell migration by 50−80%. Herein, the development of a nanotherapeutic strategy for ccRCC-specific siRNA delivery and its potential to interfere with key oncogenic pathways is presented.

NIMG-110. FIRST CLINICAL EXPERIENCE WITH BELZUTIFAN IN VON HIPPEL-LINDAU DISEASE-ASSOCIATED CNS HEMANGIOBLASTOMA

Abstract The authors present two cases of von Hippel-Lindau (VHL) disease-associated hemangioblastomas in the central nervous system (CNS) treated with the newly-approved HIF-2α inhibitor, belzutifan. The first case is that of a 31-year-old female with confirmed pathogenic germline VHL mutation who presented with multiple hemangioblastomas diagnosed at 25 years of age. The patient was first managed surgically with resection of three posterior fossa hemangioblastomas but re-presented five years later with headaches and paresthesias of the fingers. She was found to have interval progression of an intramedullary cervical lesion that was monitored radiographically, as well as a new cerebellar lesion. A cerebellar lesion was resected, but the cervical hemangioblastoma was not. Four months after surgery, the patient was started on belzutifan, which she tolerated without issue, and a brisk reduction in peri-lesional edema was observed in the cervical spine and remaining intracranial foci after 2 months of treatment. The second patient is a 30-year-old male with familial VHL disease, initially diagnosed after the discovery of a retinal hemangioblastoma at age 10. He was found to have multiple cerebellar hemangioblastomas, treated with resection at age 24 and then with stereotactic radiosurgery (SRS) at age 25, complicated by radiation necrosis. Imaging surveillance revealed disease progression at age 29 for which he was started on belzutifan. Follow-up imaging after three one month cycles revealed a reduction in perilesional edema and reduced lesion mass effect. Both patients tolerated belzutifan well, with only anemia and fatigue. We highlight in this report our initial experience and early imaging findings associated with belzutifan used for VHL disease-associated CNS hemangioblastomas.

Hypoxia-Inducible Factor 2 Alpha (HIF2α) Inhibitors: Targeting Genetically Driven Tumor Hypoxia.

Tumors driven by deficiency of the VHL gene product, which is involved in degradation of the hypoxia-inducible factor subunit 2 alpha (HIF2α), are natural candidates for targeted inhibition of this pathway. Belzutifan, a highly specific and well-tolerated HIF2α inhibitor, recently received FDA approval for the treatment of nonmetastatic renal cell carcinomas, pancreatic neuroendocrine tumors, and central nervous system hemangioblastomas from patients with von Hippel-Lindau disease, who carry VHL germline mutations. Such approval is a milestone in oncology; however, the full potential, and limitations, of HIF2α inhibition in the clinic are just starting to be explored. Here we briefly recapitulate the molecular rationale for HIF2α blockade in tumors and review available preclinical and clinical data, elaborating on mutations that might be particularly sensitive to this approach. We also outline some emerging mechanisms of intrinsic and acquired resistance to HIF2α inhibitors, including acquired mutations of the gatekeeper pocket of HIF2α and its interacting partner ARNT. Lastly, we propose that the high efficacy of belzutifan observed in tumors with genetically driven hypoxia caused by VHL mutations suggests that a focus on other mutations that similarly lead to HIF2α stabilization, such as those occurring in neuroendocrine tumors with disruptions in the tricarboxylic acid cycle (SDHA/B/C/D, FH, MDH2, IDH2), HIF hydroxylases (EGLN/PHDs), and the HIF2α-encoding gene, EPAS1, are warranted.