This is a clinical trial assessing the efficacy, safety, and tolerability of an investigational drug, VRDN-003, in participants with chronic Thyroid Eye Disease (TED).

This is a randomized (meaning participants will be assigned to study arms by chance), double-masked (meaning study doctor and participant will not know which study arm participant is assigned to), placebo-controlled study that will include participants with chronic TED. The key objectives of this study are to determine if VRDN-003 is efficacious, safe and tolerable when administered as subcutaneous/SC injections every 4 weeks or every 8 weeks compared to placebo in participants with chronic TED.

Participants who do not have a meaningful response at Week 24 (irrespective of the initial treatment arm) may be eligible to receive additional subcutaneous injections of VRDN-003.

Key Inclusion Criteria:

• Must have moderate to severe chronic TED, with any CAS (0-7) on the 7-item scale, and with documented evidence of ocular symptoms or signs that began greater than 15 months prior to screening
• Must agree to use highly effective contraception as specified in the protocol
• Female TED participants must have a negative serum pregnancy test at screening

Key Exclusion Criteria:

• Must not have received prior treatment with another anti-IGF-1R therapy
• Must not have received systemic corticosteroids or steroid eye drops for any condition, including TED, or selenium within 2 weeks prior to first dose.
• Must not have received other immunosuppressive drugs for any condition, including TED, or any other therapy for TED within 12 weeks prior to first dose
• Must not have received an investigational agent for any condition, including TED, within 8 weeks or longer duration (depending on the type of investigational agent) prior to first dose
• Must not have received radioactive iodine (RAI) treatment within 8 weeks prior to first dose
• Must not have had previous orbital irradiation or decompression surgery for TED to the study eye's orbit
• Must not have a pre-existing ophthalmic condition in the study eye which in the study doctor's opinion, would interfere with interpretation of study results
• Must not have abnormal hearing test before first dose. Must also not have a history of ear conditions considered significant by study doctor
• Must not have a history of inflammatory bowel disease
• Female TED participants must not be pregnant or breastfeeding

NOTE: There are additional eligibility criteria for participants who do not have a meaningful response at Week 24 (irrespective of initial treatment arm) who may receive additional injections of VRDN-003. These are described in the protocol.

Participants will be randomized to one of the three study arms.