New Antisense Oligonucleotide Approved for Rare Disease Treatment

The treatment landscape for transthyretin amyloidosis (ATTR), a rare but severe condition, has expanded with the recent approval of a new antisense oligonucleotide (ASO) called Eplontersen (Wainzua®). This medication is specifically designed for patients suffering from hereditary ATTR with polyneuropathy (hATTR-PN), a form of the disease that can lead to significant neurological impairment.

ATTR is caused by the misfolding of the transthyretin (TTR) protein, which is produced in the liver. This misfolded protein accumulates in various tissues, disrupting their function and potentially leading to serious complications, including heart and nerve diseases. There are both hereditary and wild-type forms of ATTR, with hATTR-PN affecting the peripheral nervous system.

Without timely treatment, the progression of hATTR-PN can lead to paralysis, requiring patients to rely on wheelchairs and bed rest, with a prognosis of 5 to 15 years without intervention. Current treatment options include other approved drugs such as Patisiran, Vutrisiran, and Inotersen, which are also aimed at managing symptoms and halting disease progression.

Eplontersen, administered subcutaneously once a month, is a novel ASO that demonstrates a targeted approach to reducing TTR production. The unique N-Acetylgalactosamine (GalNAc) conjugation allows for efficient delivery of the ASO to hepatocytes, the primary site of TTR production. By binding selectively to TTR mRNA, Eplontersen facilitates its degradation, effectively decreasing TTR synthesis.

The approval of Eplontersen is supported by data from the Phase III clinical trial known as NeuroTTRansform, which involved 144 participants with hATTR-PN. Over a 65-week period, patients received Eplontersen every four weeks, while an external placebo cohort from a previous study served as a control. Both groups had similar inclusion criteria, ensuring a robust comparison.

The primary endpoints evaluated included the percentage change in serum TTR concentration and the modified neuropathy impairment score (mNIS+7) from baseline to week 65. Results indicated that patients treated with Eplontersen experienced an approximately 80% reduction in serum TTR levels, compared to just 10% in the placebo group. Furthermore, the deterioration of neurological function was significantly less pronounced in the Eplontersen group, with a mean increase of only 3.2 points on the mNIS+7 scale, contrasting sharply with the 26.3-point increase observed in the placebo cohort.

This promising data underscores the potential of Eplontersen in altering the disease course for those affected by hATTR-PN. As healthcare providers begin to evaluate treatment options for patients in stages 1 and 2 of this condition, Eplontersen may also be continued in stage 3 under certain circumstances, provided that the benefits outweigh the associated risks.

In conclusion, the introduction of Eplontersen marks a notable advancement in the therapeutic arsenal against ATTR, offering hope to thousands of patients worldwide who are grappling with the debilitating effects of this rare disease.