Arrowhead's Plozasiran Shows Positive Phase 3 Efficacy in Severe Hypertriglyceridemia, De-Risking Expansion

What happened

Arrowhead presented 12-month Phase 3 results from its SHASTA-3 and SHASTA-4 trials for plozasiran in severe hypertriglyceridemia at the European Society of Cardiology Congress, showing substantial triglyceride reductions and lower acute pancreatitis events versus placebo. The data validate the core sHTG expansion thesis outlined in our prior report, which had assigned significant value to a successful readout in Q3 2026. Simultaneous acceptance for publication in a major medical journal adds an additional layer of peer-review validation. While full statistical details and longer-term safety remain to be scrutinized, the readout appears to clear the primary efficacy hurdle for a year-end 2026 sNDA filing. This reduces the binary outcome risk, but REDEMPLO net sales disclosure and payer-driven commercial traction remain unproven.

Implication

The positive SHASTA-3/4 data materially de-risk the sNDA filing and support the sHTG expansion valuation, but current price already reflects much of that optionality, so we would not chase above $70. The key remaining checkpoint is whether Arrowhead finally discloses REDEMPLO net sales in its next quarterly report, converting launch anecdotes into revenue evidence. If management reiterates the year-end sNDA timeline and provides tangible commercialization metrics, we would consider upgrading to BUY on weakness. If net sales disclosure is again absent or payer friction emerges, the WAIT stands with entry preference near our $55 target. Over the next 90 days, monitor quarterly revenue mix and management commentary for early signs of durable launch traction.

Thesis delta

Our previous WAIT rested on two unproven bridges: sHTG Phase 3 success and REDEMPLO net sales disclosure. The presented SHASTA-3/4 data resolve the first bridge with positive efficacy and safety signals, shifting the probability of a successful sNDA filing upward. However, the commercial proof point remains outstanding, so we raise our conviction on the sHTG catalyst but retain WAIT until net sales are disclosed or the stock offers a better entry near our $55 target.