MK-3795

This study shows that the application of similar or diverse assay protocols allows to detect various influences on HIF heterodimerization as a key signaling event in the oxygen sensing pathway: increased HIF heterodimerization (roxadustat, MG-132), decreased HIF heterodimerization (PX-478, ibuprofen) and direct (HIF isoform-selective) heterodimerization inhibiting effects (PT-2385). Specific and general considerations include cell-based, technical and disease/drug-related aspects (e.g., non-specific effects, color interference). In summary, the versatility of these bioassays offers benefits in widespread applications regarding drug discovery and pharmacological characterization of various therapeutics, applying either the same or optimized experimental protocols.

Tfeb mislocalization was reversed by hypoxia-inducible factor 2 inhibitor PT2385 and, independently, through inhibition of lactic acid production. These experimental findings were confirmed clinically in patients with Crohn's disease and through bioinformatic searches in databases from Crohn's disease or ulcerative colitis biopsies showing loss of IRP2 and transcription factor EB (TFEB)-dependent lysosomal gene expression. Overall, our study highlights a mechanism whereby Irp2 supports nuclear translocation of Tfeb and lysosomal function, preserving macrophage antimicrobial activity and protecting the liver against invading bacteria during intestinal inflammation.

P1, N=110, Active, not recruiting, Peloton Therapeutics, Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) | Trial completion date: Nov 2024 --> Nov 2026

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

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.

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.

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.

P1, N=110, Active, not recruiting, Peloton Therapeutics, Inc. | Trial completion date: Nov 2022 --> Nov 2023

We evaluated the response to several therapies: IACS-010759 (mitochondrial respiratory chain complex I inhibitor), sunitinib (tyrosine kinase inhibitor with anti-angiogenic activity), talazoparib (poly ADP ribose polymerase (PARP) inhibitor) combined or not to temozolomide (alkylating agent), pharmacological inhibitors of HIF2a (PT2385 and PT2977 (belzutifan)) and molecular inactivation of HIF2a (imCC Sdhb-/- shHIF2a). 1H-MRS, but not DCE-MRI, enabled monitoring response to sunitinib, which was the best treatment in this study, promoting a decrease in succinate levels detected in vivo. This study paves the way for new therapeutic options and reveals a potential new early biomarker of response to treatment in SDHB-dependent PPGL.

In addition, the combination of DOX and PT-2385 could jointly inhibit VEGF expression, which was another reason accounting for the combined anti-cancer effect of PT/DOX-MS. Overall, our study demonstrated that PT/DOX-MS is a promising embolic agent for enhanced HCC treatment via the combined effect of hypoxia microenvironment improvement, chemotherapy, and embolization.

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.

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

The PT-2385-mediated block of I in GH cells was little-affected by the further application of diazoxide, cilostazol, or sorafenib. Alternatively, the presence of PT-2385 in human 13-06-MG glioma cells effectively decreased the amplitude of I. Considering all of the experimental results together, the effects of PT-2385 on ionic currents demonstrated herein could be non-canonical and tend to be upstream of the inhibition of HIF-2α. This action therefore probably contributes to down-streaming mechanisms through the changes that it or other structurally resemblant compounds lead to in the perturbations of the functional activities of pituitary cells or neoplastic astrocytes, in the case that in vivo observations occur.

P1, N=50, Recruiting, Neil M Rofsky, MD, MHA | Not yet recruiting --> Recruiting

P1, N=50, Not yet recruiting, Neil M Rofsky, MD, MHA

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.

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.

Furthermore, the finding of a hypomorphic ventilatory phenotype in untreated HIF-2α S305M mutant mice suggests a function for the HIF-2α PAS-B domain beyond heterodimerisation with HIF-1β. Although PT2385 was well-tolerated, the findings indicate the need for caution in patients who are dependent on hypoxic ventilatory drive.