The purpose of this study is to assess the safety and efficacy of extended dosing with IONIS GHR-LRx in participants with acromegaly as add-on to somatostatin receptor ligands (SRL) therapy.

This extension study will include participants up to 60 participants with acromegaly from Study NCT03548415. All participants will remain on the same dose from the previous study and receive IONIS GHR-LRx (SC) injection once every 28 days as add-on to SRL therapy for 53 weeks. At the end of 53 weeks, participants will enter a 14-week post-treatment (PT) evaluation period.

Inclusion Criteria:

• Randomized in index trial (CS2) and completed the entire study, or completion of the treatment period for CS2 and completed or plan to complete PTWK5 visit with an acceptable safety profile, per investigator judgment
• Participants with confirmed stable monthly regimen of SRL for 3 months prior to screening
• Able and willing to participate in a 53-week treatment and 14-week post-treatment study

Exclusion Criteria:

• Treatment with any other acromegaly medications taken prior to Day 1 within the time period: bromocriptine: 2 weeks, carbergoline: 4 weeks, quinagolide: 4 weeks, pegvisomant: 4 weeks and pasireotide: 4 months
• Participant who received surgery for pituitary adenoma in the last 3 months prior to screening and participants needing and/or planning to receive surgery for the pituitary adenoma during the trial
• Unwilling to comply with required study procedures during the treatment and post-treatment periods