This multicenter post-trial access program is designed to provide ATH434 orally BID to eligible patients who completed Phase 2 studies ATH434-201 or ATH434-202, and who may benefit from this treatment according to the evaluation by their treating physicians.

This multicenter PTA program is designed to provide ATH434 orally BID to eligible patients who have completed the ATH434-201 or ATH434-202 Phase 2 clinical trials, and who may benefit from this treatment according to evaluation by their treating physician. Up to 20 patients will be enrolled in the US.

For each patient, treating physicians will request participation in the PTA study and initial ATH434 shipment for patients who meet entry criteria. Upon review and approval by the Medical Monitor/Sponsor, treating physicians will obtain informed consent from the patient and proceed with ATH434 initiation under the PTA program. Pertinent documented medical information will be requested to confirm eligibility and assess patient safety throughout the PTA program.

Eligible patients will receive ATH434 tablets BID to be taken with food for up to 12 months, and will complete in-clinic and remote visits for safety and to dispense/return ATH434.

Inclusion Criteria:

• Completed Alterity protocol ATH434-201 or ATH434-202
• Expected to benefit from treatment from treatment with ATH434, in the opinion of the treating physician

Exclusion Criteria:

• Discontinued prior ATH434 treatment (ATH434-201 or ATH434-202) for any reason
• Significant medical or psychiatric condition that may decrease the benefit-risk ratio of participation in this program to an unacceptable level, as per the treating physician's opinion