ARO-HIF2 is an siRNA drug designed to selectively target hypoxia-inducible factor-2α (HIF2α) interrupting downstream pro-oncogenic signaling in clear cell renal cell carcinoma (ccRCC)...Further development was hampered by off-target neurotoxicity and low response rate. This study provides proof of concept that siRNA can target tumors in a specific manner.

Moreover, HIFα negatively regulates the expression of FKBP10, and inhibition of FKBP10 enhances the antitumor effect of the HIF2α inhibitor PT2385. Therefore, our study demonstrates that FKBP10 promotes clear cell renal cell carcinoma progression and regulates sensitivity to HIF2α blockade by facilitating LDHA phosphorylation, which may be exploited for anticancer therapy.

P1, N=110, Active, not recruiting, Peloton Therapeutics, Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) | Trial completion date: Nov 2023 --> Nov 2024

P2, N=4, Completed, Peloton Therapeutics, Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) | Active, not recruiting --> Completed | Trial primary completion date: Nov 2023 --> Aug 2023

Nanocarrier-loaded PT2399 prevented radiation-induced bone loss in mice while reducing drug accumulation in the kidney. Targeted inhibition of HIF-2α may represent a therapeutic approach for protecting bone during radiation therapy.

PT2385 monotherapy had limited activity in first recurrent GBM. Drug exposure was variable. Signals of activity were observed in GBM patients with high systemic exposure and acidic lesions on CEST imaging. A second-generation HIF2α inhibitor is being studied.

P1, N=146, Recruiting, Arcus Biosciences, Inc. | N=86 --> 146

P1, N=24, Completed, Arcus Biosciences, Inc. | Recruiting --> Completed

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.

ALI cultures were exposed to conditioned medium from EGJ fat of obese patients (CM-EGJ) with or without PT2385 (a HIF-2α specific inhibitor), or to control medium (CtrlM); we measured transepithelial resistance (TER, an index of barrier function) in ALI cultures on days 4, 6, and 8... Substances produced by EGJ fat of obese subjects impair esophageal barrier function and cause esophageal squamous cells to secrete the pro-inflammatory cytokine IL-1β via activation of HIF-2α. This suggests that, in obesity, visceral fat induces HIF-2α-dependent activation of caspase-1 to cause a GERD-independent esophageal inflammatory response that impairs esophageal barrier function.

In conclusion, HIF-2α knockout could inhibit the function of LSCs by affecting their metabolic pattern and vascular microenvironment in CML. Therefore, targeting HIF-2α may become a new strategy, and its specific inhibitor PT2399 may be a candidate drug for clinical application in CML treatment.

We inhibited HIF-2α expression in the Insufficient RFA group using PT2385 and assessed the resulting changes in proliferation and biological function of HCCs...Insufficient ablation increased the mRNA and protein expression of VEGF, HIF-2α, and Notch1 in HCCs, whereas inhibition of HIF-2α reversed these changes. Insufficient RFA increases the proliferation, migration, and invasion of HCCs via the HIF-2α/VEGF/Notch1 signaling axis; HIF-2α is a potential target for novel treatments of HCC after insufficient RFA.

In this first-in-human study, AB521 demonstrated PK/PD properties that are consistent with a potential best-in-class HIF-2α profile.

Inhibition of HIF2α with the small-molecule PT2399 prevented prostate cancer cell proliferation. Inhibition of HIF2α with the small molecule PT2399 prevented prostate cancer cell proliferation. These results thus identify HIF2α as a regulator of androgen synthesis and potential therapeutic target in prostate cancer.

Together, these data suggest that stromal HIF2 is an essential component of PDAC pathobiology and is a druggable therapeutic target that could relieve tumor microenvironment immunosuppression and enhance immune responses in this disease.

No abstract available

• [Ga]Ga-PSMA-11 PET/CT could potentially predict the HIF-2α expression of primary tumors among patients with RCC. • SUVof [Ga]Ga-PSMA-11 PET/CT was the most significant predictor of HIF-2α expression level. • This probability could help predict the therapeutic response of patients with RCC to HIF-2α antagonists.

Referring herein to both first- and second-generation (ARO-HIF2) siRNA drugs, siHIF2 is specifically taken up by human ccRCC tumors transplanted in mice, where it depletes HIF2a inhibiting target gene expression and tumor growth...siHIF2 has activity against both wild-type and drug-resistant mutant HIF2a and is expected to be active in patients progressing on PT2977 (belzutifan), a PT2399-related drug recently approved by the FDA. To our knowledge, this is the first example of functional inactivation of an oncoprotein with a tumor-directed siRNA in humans. In summary, these studies provide unique insight into HIF2a (the only known core dependency in ccRCC), illustrate how it can be effectively inhibited by an siRNA drug, and establish a paradigm for the development of tumor directed siRNA-based therapeutics.

While as a transcription factor HIF2a had escaped drug targeting, structural studies revealed an unusual cavity, which became the foundation for the development of small molecule inhibitors such as PT2385 (a first-in-class drug), or the related PT2399 tool compound and the recently FDA-approved PT2977 (also called belzutifan). Reporting on a hypoxia sensor, a HIF2a radiotracer may be a useful ischemia probe. In summary, we report the development of a novel radiotracer with extensive potential applications currently being evaluated in humans.

One pt (cohort 2, with prior sunitinib, nivolumab, axitinib) experienced a partial response with 66% reduction in sum of longest diameters. HIF2a is a clinically validated driver of ccRCC which can be targeted with a RNAi therapeutic. This ongoing phase 1 study provides initial proof of target engagement based on reductions in HIF2a expression as well as a favorable safety profile in response to escalating doses of ARO-HIF2.

In conclusion, Mut-VHL ccRCC cells displayed higher PD-L1 expression due to high basal HIF2α expression and a stronger response to IFNγ stimulation than WT-VHL cells. The fact that HIF2α antagonists can potentially reduce PD-L1 expression levels should be considered in ICI combination therapy.

this study shows key differences between inhibiting a target versus knockdown, which are potentially targetable.

Here we investigated the effects on tumor growth and on the tumor microenvironment of three different direct and indirect HIF-α inhibitors, namely the HIF-2α-specific inhibitor PT2399, the dual HIF-1α/HIF-2α inhibitor Acriflavine, and the S1P signaling pathway inhibitor FTY720, in the autochthonous Vhl/Trp53/Rb1 mutant ccRCC mouse model and validated these findings in human ccRCC cell culture models. We also identify that HIF-2α inhibition strongly suppresses T cell activation in ccRCC. These findings suggest prioritization of sphingosine pathway inhibitors for clinical testing in ccRCC patients and also suggest that HIF-2α inhibitors may inhibit anti-tumor immunity and might therefore be contraindicated for combination therapies with immune checkpoint inhibitors.

MiR-519d-3p was downregulated in NSCLC patients with poor response to gefitinib. Targeting miR-519d-3p/EPAS1 axis may provide alternative treatment for TKI-resistant NSCLC.

Moreover, pharmacological inhibition of SCARB1 using a novel compound (ITX-5061) results in decreased ccRCC cell proliferation in vitro...The impact of this KCRP Idea Development Application comes from the pressing need for new therapeutic strategies, given that targeted therapies, anti-angiogenics, immunotherapies, and other metabolic strategies (such as targeting glutamine metabolism) only serve subsets of patients, even in combination, and altered cholesterol metabolism is a universal feature of ccRCC. Finally, as HIF-2alpha antagonists continue to be tested in ongoing clinical trials, SCARB1 inhibition could be deployed in patients ultimately acquiring resistance to HIF-2alpha-specific drugs, as previously demonstrated in preclinical studies.

The objective response rate was 25% in 55 patients with clear cell renal cell carcinoma (ccRCC).

No difference in animal survival was seen in combination treatment with radiation (RT)/temozolomide (TMZ)/PT2385 (p = 0.44, n = 10) or mean tumor bioluminescence (t 1.13, p = 0.32). PT2385 as a single-agent was efficacious in vivo, however, an increase in animal survival was not seen with PT2385 in combination with RT/TMZ. Further study for targeting HIF2α as a therapeutic approach in GBM is warranted.

P3, N=708, Recruiting, Merck Sharp & Dohme Corp. | Not yet recruiting --> Recruiting

In the first study of a novel HIF2a inhibitor in patients with VHL, PT2385 demonstrated stabilization of disease in VHL-associated clear cell RCC and other tumors, and showed an acceptable safety profile. Further evaluation of this class of agents in VHL is warranted, and a second-generation HIF-2α inhibitor is currently the subject of a phase 2 trial in this population.Funding: This research was supported by the Intramural Research Program of the NIH, Urologic Oncology Branch. Author LM was funded by NCI Contract No.

The lack of effect from PT2385 treatment in combination with high cytoplasmic HIF-2α expression at normoxia suggest that HIF-2α have additional roles than acting as an ARNT dependent transcription factor. It is important to further unravel the conditions at which HIF-2α has transcriptional and non-transcriptional roles in neuroblastoma.

P3, N=708, Not yet recruiting, Merck Sharp & Dohme Corp.

Funding: Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Clinical trial identification: NCT03401788.

Key secondary endpoints include objective response rate, duration of response, patient-reported outcomes, and safety. Research Funding: Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA