Design: Prespecified subgroup analysis of the HELIOS-B randomised trial
Population: 654 adults with transthyretin amyloid cardiomyopathy, 40% on background tafamidis
Primary outcome: All-cause mortality and recurrent cardiovascular events, by baseline tafamidis use
Effect: Rate ratio 0.79 (95% CI 0.51-1.21) on tafamidis vs 0.67 (0.49-0.93) without; no significant interaction

This prespecified subgroup analysis of HELIOS-B looked at whether vutrisiran, an RNA-interference therapy that lowers hepatic transthyretin, worked differently depending on whether patients were already taking the stabiliser tafamidis. Of 654 patients with transthyretin amyloid cardiomyopathy, 40% were on tafamidis at baseline.

The effect on the primary composite of death and recurrent cardiovascular events pointed the same way in both groups: a rate ratio of 0.79 in those on tafamidis and 0.67 in those not, with no statistically significant interaction. The effect was numerically smaller among patients already on a stabiliser, and the improvement in quality-of-life score looked attenuated there.

This supports starting vutrisiran regardless of existing tafamidis, but it is a subgroup comparison, not a trial of combination therapy. Whether adding vutrisiran to a stabiliser gives extra benefit over either alone needs a dedicated trial.

Prespecified subgroup analysis of HELIOS-B in 654 patients with ATTR cardiomyopathy.
40% were taking the stabiliser tafamidis at baseline.
Vutrisiran's effect on death and cardiovascular events was directionally consistent in both groups.
The rate ratio was 0.79 on tafamidis versus 0.67 without, with no significant interaction.
The benefit looked numerically smaller in those already on a stabiliser.

Why it matters

It addresses the common question of whether to start an RNA-interference agent in a patient already stabilised, without settling whether combination is better.

The statistics, in plain English

A non-significant interaction (p=0.55) means the trial could not show the drug works differently with or without tafamidis, but with only 654 patients split into subgroups it was not powered to detect a modest difference either way.