Inclusion Criteria:

1. Satisfactory completion of ION-682884-CS3 (NCT04136184) (Index Study) as judged by the
Investigator and Sponsor, or diagnosis of hATTR-PN and satisfactory completion of
either study ISIS 420915-CS101 or study 2018-P001436 (NCT03702829) (both are
Investigator-Sponsored studies with inotersen - the unconjugated version of
Eplontersen) as judged by the Investigator and Sponsor.

2. Must have given written informed consent (signed and dated) and any authorizations
required by local law and be able to comply with all study requirements.

3. Satisfy the following:

1. Females: must be non-pregnant and non-lactating and either:

- Surgically sterile (e.g., tubal occlusion, hysterectomy, bilateral
salpingectomy, bilateral oophorectomy);

- Post-menopausal (defined as 12 months of spontaneous amenorrhea in females >
55 years of age or, in females ≤ 55 years, 12 months of spontaneous
amenorrhea without an alternative medical cause and follicle-stimulating
hormone (FSH) levels in the postmenopausal range for the laboratory
involved;

- Abstinent*;

- If engaged in sexual relations of child-bearing potential, agree to use
highly effective contraceptive methods from the time of signing the informed
consent form until at least 24 weeks after the last dose of Eplontersen and
agree to receive pregnancy tests per protocol.

2. Males: Surgically sterile (i.e., bilateral orchidectomy) or abstinent*, if
engaged in sexual relations with a woman of child-bearing potential (WOCBP), the
participant or the participant's non-pregnant female partner must use a highly
effective contraceptive method from the time of signing the informed consent form
until at least 24 weeks after the last dose of Eplontersen. *Abstinence (i.e.,
refraining from heterosexual intercourse throughout the duration of study
participation) is only acceptable as true abstinence, i.e., when this is in line
with the preferred and usual lifestyle of the participant. Periodic abstinence
(e.g., calendar, ovulation, symptothermal, post-ovulation methods), declaration
of abstinence for the duration of a trial and withdrawal are not acceptable
methods of contraception.

4. Willingness to adhere to vitamin A supplementation per protocol.

Exclusion Criteria:

1. Have any new condition or worsening of existing condition that in the opinion of the
Investigator or Sponsor would make the participant unsuitable for enrollment or could
interfere with the participant taking part in or completing the study.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 11/2/22. Questions regarding updates should be directed to the study team contact.