- Design
- Prespecified subgroup analysis of a phase 3 randomised placebo-controlled trial
- Population
- 654 people with ATTR cardiomyopathy; 259 on tafamidis at baseline
- Primary outcome
- All-cause mortality and recurrent cardiovascular events
- Effect
- Rate ratio 0.79 (0.51–1.21) with tafamidis vs 0.67 (0.49–0.93) without; P interaction 0.55
HELIOS-B randomised 654 people with transthyretin amyloid cardiomyopathy to vutrisiran 25 mg every three months or placebo for up to 36 months, and allowed background tafamidis, which 40% were taking. This prespecified analysis looked at whether vutrisiran's effect differed by tafamidis use.
For death and recurrent cardiovascular events the rate ratio was 0.79 (95% CI 0.51–1.21) in those on tafamidis and 0.67 (0.49–0.93) in those not, with no significant interaction (P = 0.55). The same pattern held for mortality, cardiovascular events and outpatient worsening heart failure. Walk distance was preserved in both groups, but the quality-of-life benefit looked smaller on tafamidis.
The honest reading is that combination therapy is neither proven nor ruled out. The confidence interval in the tafamidis group crosses 1, and the effect was numerically smaller. Those already on tafamidis were younger and fitter at baseline. Cost matters too: both drugs are very expensive, and access in India is limited.
- Do not assume adding vutrisiran to tafamidis gives the full benefit seen with vutrisiran alone.
- Discuss combination therapy as unproven, pending prospective trials designed to test it.
- Consider vutrisiran as a first-line option in ATTR cardiomyopathy where it is available, on the strength of HELIOS-B overall.
- Factor cost and access into any decision to combine two high-cost therapies.
Why it matters
Clinicians already treating with tafamidis are being asked whether to add an expensive silencer, and this is the only randomised evidence so far.
Don't overread it
A subgroup within one trial cannot establish that combination therapy works.
The statistics, in plain English
No significant interaction means the trial cannot tell the two groups apart, not that the effect is identical. With an interval of 0.51 to 1.21 in the tafamidis group, the data allow anything from a large added benefit to none.
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