858 Therapeutics Expanded Access / Compassionate Use Policy Template

858 Therapeutics is a clinical-stage drug discovery and biotechnology company developing a portfolio of small-molecule drugs that act on novel therapeutic targets in oncology and immunology.

This policy explains how physicians may request expanded access (“compassionate use”) from 858tx for its investigational medical product when no comparable or alternative therapy options are available for seriously ill patients who are not eligible for ongoing clinical trials.

Expanded access may be considered only when all of the following conditions are met:

• The patient has a serious or immediately life-threatening disease or condition with no comparable or satisfactory alternative therapies available.
• The potential benefit to the patient justifies the potential risks of treatment based on available clinical data and the treating physician's assessment.
• The patient is ineligible for, unable to access, or has completed participation in a clinical trial involving the investigational product.
• Providing the investigational product will not negatively impact broader patient access by delaying or interfering with clinical trials, regulatory review, or product development.
• A licensed treating physician is responsible for patient care, monitoring, and safety reporting.
• All FDA, legal, regulatory, and ethics requirements are met.

858 Therapeutics evaluates each expanded access request individually. Approval in one case does not guarantee approval in others. Decisions depend on patient-specific circumstances, evolving clinical data, available supply, and overall development plans.

Requests must be submitted by a licensed treating physician. The physician must:

• Provide sufficient clinical information for evaluation.
• Obtain all required regulatory (i.e., FDA EAP Submission) and institutional approvals.
• Secure informed consent from the patient.
• Ensure appropriate monitoring and safety reporting throughout treatment.

Licensed treating physicians may submit expanded access requests to:

Email: etx-19477-101_study@8five8tx.com

858 Therapeutics will use reasonable efforts to acknowledge requests within 10 business days.

This policy will be re-evaluated periodically. 858 Therapeutics may modify or terminate the policy at any time based on emerging clinical data, regulatory changes, or business considerations.

More information about 858's ongoing clinical trial can be found at https://clinicaltrials.gov/study/NCT06395519.