Investigational RNA Interference Therapy, ARO-HIF2, Yields Encouraging Phase 1 Results in Clear Cell RCC


Patients with clear cell renal cell carcinoma experienced reduced levels of hypoxia inducible factor-2 alpha expression following treatment with ARO-HIF2.

Not only did ARO-HIF2, an investigational RNA interference (RNAi) therapy, reduce levels of hypoxia inducible factor-2 alpha (HIF2α) expression in patients with clear cell renal cell carcinoma (RCC), the agent was also found to have a manageable safety profile, according to data from the phase 1b AROHIF21001 trial (NCT04169711).1

Findings from the trial, which were presented during the 2022 Genitourinary Cancers Symposium, showed that of 26 evaluable patients, 9 experienced a median reduction in HIF2α mRNA of 30% (range, -19% to -59%) by qPCR.

In the subset of patients who received ARO-HIF2 at 225 mg (n = 7) the median reduction in HIF2α mRNA was 46% (range, -22 to -47). In those who were administered 525 mg of ARO-HIF2 (n = 10), the median reduction in HIF2α mRNA was 27% (range, -19 to -39). In the subset of patients who were given 1050 mg of the agent (n = 9), the median reduction in HIF2α mRNA was 44% (range, -28 to -49).

Additionally, 14 patients achieved a median reduction in HIF2α protein of 26% (range, -1700 to -98) by immunohistochemistry (IHC). The HIF2α protein reduction rates in the 225-mg, 525-mg, and 1050-mg cohorts were 26% (range, -26 to -82), 47% (range, 0 to -90), and 0% (range, 1700 to -98), respectively.

“This ongoing phase 1 study provides initial proof of target engagement based on reductions in HIF2α expression, as well as an acceptable safety profile in response to escalating doses of ARO-HIF2,” lead study author James Brugarolas, MD, PhD, of UT Southwestern Medical Center, and colleagues, wrote in a poster on the findings.

HIF2α is usually expressed at low levels and targeted for degradation by the von Hippel-Lindau (VHL) tumor suppressor protein. However, VHL inactivation, which is a causative event of clear cell RCC, prompts tumorigenesis through uncontrolled HIF2α accumulation. The synthetic double-stranded RNAi trigger, ARO-HIF2, which includes an alpha-v beta3 targeting ligand, was developed to silence HIF2α expression.

The AROHIF21001 trial enrolled patients with advanced or metastatic clear cell RCC that progressed during or after at least 2 prior regimens which must have included a VEGF-targeted therapy and a checkpoint inhibitor therapy.2 To be eligible for participants, patients needed to be at least 18 years of age, have an ECOG performance status of 0 or 1, a life expectancy that was longer than 3 months, and organ function that was considered to be acceptable at the time of the screening.

Exclusion criteria included a history of untreated brain metastases, having received prior systematic therapy or radiation therapy within 2 weeks of the first dose of study treatment, or having previously undergone solid organ or stem cell transplantation. Moreover, patients could not be receiving current treatment with immune checkpoint inhibitors, nor could they have received prior HIF2 inhibitors within 6 months before their first dose of study treatment.

Intravenous ARO-HIF2 was administered weekly at 225 mg in cohort 1 (n = 7), 525 mg in cohort 2 (n = 10), and 1050 mg in cohort 3 (n = 9). Moreover, tumor growth was evaluated by biopsy at baseline and again at 2 weeks. Additionally, patients were evaluated for safety each week. Every 8 weeks, participants were examined for tumor response by RECIST criteria.

The primary end point of the study was to evaluate treatment-emergent adverse effects (TEAEs) associated with ARO-HIF2. Secondary end points included pharmacokinetics and preliminary efficacy per RECIST v1.1 criteria.

Exploratory end points included the assessment of post-dose tumoral expression of HIF genes in response to treatment with the agent, change in tumor integrin expression, correlation of integrin expression with changes in HIF gene expression, and the examination of serum biomarkers of agent activity. The correlation of disease-related gene expression to the activity of the agent is also under exploration. Plasma and urine metabolites will also be assessed.

Spanning cohorts, the mean age was 65.1 years (range, 44-87). Seventy-seven percent of patients were male. Regarding performance status, 42.3% of patients had an ECOG performance status of 0, and 57.7% had a status of 1. Most patients (53.8%) had intermediate-risk disease per International Metastatic RCC Database Consortium criteria; 23.1% had good-risk disease and 15.4% had poor-risk disease.

Additionally, 30.8% of patients received 2 prior lines of therapy, 30.8% received 3 prior lines, and 11.5% received 4 prior lines of therapy. Notably, 26,9% of patients received 5 or more prior lines of treatment. Prior treatment included anti-VEGF therapy (100%) and checkpoint inhibition (100%). Regarding VHL mutation status, 17.6% of patients had frame shift mutations, 29.4% had missense mutations, 5.9% had in frame deletion, 11.8% had no variant, and 35.3% did not have this information available.

Prior data from the trial showcased early signals of activity with ARO-HIF2 in the 225 mg and 525 mg cohorts.3 Specifically, 7 of 9 patients who had evaluable tumor samples and received treatment experienced reductions in HIF2α per IHC H-score. Notably, these reductions ranged from -9% to -82%, with a mean reduction of -48%.

Additional data presented during the 2022 Genitourinary Cancers Symposium showed that ARO-HIF2 elicited an objective response rate of 7.7% in all patients, with 2 patients experiencing a partial response. Furthermore, 30.8% of patients achieved stable disease and 50.0% experienced disease progression. One patient was not evaluable for response, and response data were missing for 2 patients. Overall, the disease control rate with the agent was 38.5%.

At least 1 TEAE of any grade occurred in 96.2% of patients. Specifically, 57.7% of patients experienced at least 1 grade 1 or 2 TEAE, 30.8% reported at grade 3 TEAE, 3.8% experienced a grade 4 TEAE, and 3.8% experienced a grade 5 TEAE. Serious TEAEs were reported in 34.6% of patients. Moreover, treatment-related AEs of any grade occurred in 65.4% of patients. One patient discontinued treatment due to TEAEs.

TEAEs of any grade that occurred in more than 4 patients included fatigue (50.0%), dizziness (26.9%), dyspnea (26.9%), nausea (23.1%), abdominal pain (23.1%), neuropathy (19.2%), and constipation (19.2%).

Enrollment for the phase 1 trial remains open and enrollment is ongoing.


  1. Brugarolas J, Beckermann KE, Rini BI, et al. Initial results from the phase 1 study of ARO-HIF2 to silence HIF2-alpha in patients with advanced ccRCC (AROHIF21001). J Clin Oncol. 2022;40(suppl 6):339. doi:10.1200/JCO.2022.40.6_suppl.339
  2. Study of ARO-HIF2 in patients with advanced clear cell renal cell carcinoma. Updated April 19, 2021. Accessed May 3, 2022.
  3. Arrowhead announces positive interim results from phase 1b study of ARO-HIF2 for treatment of clear cell renal cell carcinoma. News release. Arrowhead Pharmaceuticals, Inc. July 6, 2021. Accessed May 3, 2022.
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