Phase 2 Trial of Investigational Hypertension Injection Tonlamarsen Reveals Persistent Protein Suppression but Conflicting Blood Pressure Data

ACC.26 trial of injectable tonlamarsen shows significant protein reduction, but an unexpectedly long-lasting effect masks clear blood pressure benefits.

By: AXL Media

Published: Mar 30, 2026, 4:19 AM EDT

Source: Information for this report was sourced from American College of Cardiology

A Complex Biological Response in Treatment Resistant Hypertension

The search for new ways to manage uncontrolled high blood pressure has encountered a scientific puzzle with the latest data on the investigational drug tonlamarsen. According to Luke Laffin, a cardiologist at Cleveland Clinic, the drug successfully targets angiotensinogen—the precursor protein to the hormones that regulate blood pressure—but its clinical impact remains difficult to categorize. While the medication achieved a massive and sustained drop in the target protein, the corresponding drop in blood pressure did not vary between the treatment and placebo groups as expected. This suggests that the drug's influence on the body's internal pressure-regulating systems may be far more persistent than originally hypothesized, lasting weeks or even months after a single dose.

Targeting the Renin-Angiotensin System via Monthly Injection

Tonlamarsen belongs to a new class of therapies designed for the nearly 50% of U.S. adults who struggle with uncontrolled hypertension despite taking multiple oral medications. Administered as a monthly injection, the drug works high up in the biological chain by suppressing the production of angiotensinogen in the liver. By reducing this precursor, the body produces less angiotensin, the hormone responsible for constricting blood vessels and raising pressure. The Phase 2 trial enrolled over 200 patients who were already taking between two and five different blood pressure medications but still maintained dangerously high systolic readings, averaging 147 mmHg.

Analyzing the Divergent Results of the Kardinal Phase 2 Trial

The study's primary endpoints focused on both protein levels and clinical blood pressure readings at the 20-week mark. While those who continued receiving monthly tonlamarsen saw a 67.2% reduction in angiotensinogen, those who switched to a placebo after the first month still saw a 23% reduction. More surprisingly, both groups experienced an identical 6.7 mmHg drop in systolic blood pressure that was maintained through the end of the trial. This suggests that even a single initial dose of the drug was powerful enough to lower blood pressure and keep it lowered for four months, regardless of whether the patient received subsequent active injections.