Lower BP and Better Tumor Control With Drug Combo?

Neil Osterweil

October 22, 2020

It's not ready for the clinic, but new research suggests that angiotensin receptor II blockers (ARBs) widely used to treat hypertension may improve responses to cancer immunotherapy agents targeted against the programmed death-1/ligand-1 (PD-1/PD-L1) pathway.

That conclusion comes from an observational study of 597 patients with more than 3 dozen different cancer types treated in clinical trials at the US National Institutes of Health. Investigators found that both objective response rates (ORR) and 3-year overall survival (OS) rates were significantly higher for patients treated with a PD-1/PD-L1 inhibitor who were on ARBs compared with patients who weren't taking the antihypertensive agents.

An association was also seen between higher ORR and OS rates for patients taking angiotensin converting enzyme (ACE) inhibitors — but it was not statistically significant, reported Julius Strauss, MD, from the Center for Cancer Research at the National Cancer Institute (NCI) in Bethesda, Maryland.

All study patients received PD-1/PD-L1 inhibitors and the ORR for patients treated with ARBs was 33.8%, compared with 19.5% for those treated with ACE inhibitors, and 17% for those who took neither drug. The respective complete response (CR) rates were 11.3%, 3.7%, and 3.1%.

Strauss discussed the data during an online briefing prior to his presentation of the findings during the 32nd EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics, which is taking place virtually.

Several early studies have also suggested that angiotensin II, in addition to its effect on blood pressure, can also affect cancer growth by leading to downstream production of two proteins: vascular endothelial growth factor (VEGF) and transforming growth factor beta (TGF-β), he explained.

"Both of these [proteins] have been linked to cancer growth and cancer resistance to immune system attack," Strauss observed.

He also discussed the mechanics of possible effects. Angiotensin II increases VEGF and TGF-β through binding to the AT1 receptor, but has the opposite effect when it binds to the AT2 receptor, resulting in a decrease in both of the growth factors, he added.

ACE inhibitors prevent the conversion of angiotensin I to angiotensin II, with the result being that the drugs indirectly block both the AT1 and AT2 receptors.

In contrast, ARBs block only the AT1 receptor and leave the AT2­ counter-regulatory receptor alone, said Strauss.

More Data, Including on Overall Survival

Strauss and colleagues examined whether ACE inhibitors and/or ARBs could have an effect on the response to PD-1/PD-L1 immune checkpoint inhibitors delivered with or without other immunotherapies, such as anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) checkpoint inhibitors, or targeted agents such as tyrosine kinase inhibitors (TKIs).

They pooled data on 597 patients receiving PD-1/PD-L1 inhibitors in clinical trials for various cancers, including 71 receiving concomitant ARBs, 82 receiving an ACE inhibitor, and 444 who were not receiving either class of antihypertensives.

The above-mentioned improvement in ORR with ARBs compared with patients not receiving the drug was statistically significant (P = .001), as was the improvement in CR rates (P = .002). In contrast, neither ORR nor CR were significantly better with patients on ACE inhibitors compared with patients not taking these drugs.

In multiple regression analysis controlling for age, gender, body mass index (BMI), tumor type, and additional therapies given, the superior ORR and CR rates with ARBs remained (P = .039 and .002, respectively), while there continued to be no significant additional benefit with ACE inhibitors.

The median overall survival was 35.2 months for patients on ARBs, 26.2 months for those on ACE inhibitors, and 18.8 months for patients on neither drug. The respective 3-year overall survival rates were 48.1%, 37.2%, and 31.5%, with the difference between the ARB and no-drug groups being significant (P = .0078).

In regression analysis controlling for the factors mentioned before, the OS advantage with ARBs but not ACE inhibitors remained significant (P = .006 for ARBs, and .078 for ACE inhibitors).

Strauss emphasized that further study is needed to determine if AT1 blockade can improve outcomes when combined anti-PD-1/PD-L1-based therapy.

It might be reasonable for patients who are taking ACE inhibitors to control blood pressure and are also receiving immunotherapy with a PD-1/PD-L1 inhibitor to be switched to an ARB if it is deemed safe and if further research bears it out, said Strauss in response to a question from Medscape Medical News.

Hypothesis-Generating Study

Meeting co-chair Emiliano Calvo, MD, PhD, from Hospital de Madrid Norte Sanchinarro in Madrid, Spain, who attended the media briefing but was not involved in the study, commented that hypothesis-generating research using drugs already on the market for other indications adds important value to cancer therapy.

James Gulley, MD, PhD, from the Center for Cancer Research at the NCI, also a meeting co-chair, agreed with Calvo.

"Thinking about utilizing the data that already exists to really get hypothesis-generating questions, it also opens up the possibility for real-world data, real-world evidence from these big datasets from [electronic medical records] that we could really interrogate and understand what we might see and get these hypothesis-generating findings that we could then prospectively evaluate," Gulley said.

The research was funded by the National Cancer Institute. Strauss and Gulley are NCI employees. Calvo disclosed no relevant financial relationships.

32nd EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics: Abstract 7. Presented in a briefing October 20 and in a plenary session October 25, 2020.

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