This is a multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trial designed to evaluate the efficacy and safety of efavirenz in patients with Creutzfeldt-Jakob disease (CJD). A total of 246 eligible participants will be enrolled across 21 study centers nationwide. Participants will be randomly assigned in a 1:1 ratio to receive either efavirenz or placebo.

Participants in the efavirenz group will receive 200 mg once daily at bedtime for the first week, followed by an increased dose of 400 mg once daily thereafter. Participants in the placebo group will receive matching placebo tablets using the same dosing schedule. Treatment will be administered under double-blind conditions and will continue until death or study completion.

During the study, all participants will receive monthly telephone follow-up assessments starting from treatment initiation to evaluate long-term efficacy and safety, continuing until death or study termination.

The primary objective of the study is to determine whether efavirenz can prolong survival in patients with CJD. The primary endpoint is median survival time from randomization to death. Secondary endpoints include assessment of the effect of efavirenz on the rate of functional decline and treatment tolerability. Adverse events (AEs) and serious adverse events (SAEs) will be recorded and evaluated for frequency, severity, outcomes, and their relationship to the study drug.

Key inclusion criteria include adults aged 18 to 80 years of either sex with a baseline MRC-Prion Disease Rating Scale (MRC-PDRS) score greater than 10 and the availability of a reliable caregiver to support study participation. Key exclusion criteria include the presence of other serious or life-threatening illnesses, use of medications contraindicated with efavirenz that cannot be adjusted, and pregnancy or breastfeeding. Written informed consent will be obtained from all participants or their legally authorized representatives prior to enrollment.

Inclusion Criteria:

• Patients who meet the World Health Organization (WHO) diagnostic criteria for probable sporadic CJD or have a genetically confirmed diagnosis of hereditary CJD.
• Age 18-80 years, any sex.
• Baseline score on the Medical Research Council Prion Disease Rating Scale (MRC-PDRS) >10 (i.e., retaining some functional ability).
• The patient has a caregiver aged ≥18 years who can accompany the patient during the study and assist in providing relevant information.
• The patient or their legally authorized representative has signed the informed consent form.

Exclusion Criteria:

• Presence of severe somatic diseases or unstable clinical conditions that may affect study compliance or patient safety, including malignancy, advanced liver or kidney dysfunction, severe cardiac disease (including patients with a history of significant QTc prolongation).
• Current use of drugs that are known contraindications with efavirenz and cannot be discontinued or substituted.
• Female participants who are pregnant or breastfeeding.
• Other medical or psychiatric conditions, as judged by the investigator, that may interfere with the patient's participation in or completion of the study.

The results of this study will be summarized promptly after study completion, with consideration given to publication in academic journals. Any publication will adhere to ICMJE guidelines regarding authorship and disclosure of conflicts of interest. Regardless of whether the study results are positive or negative, they will be reported on public platforms (e.g., updates on the Chinese Clinical Trial Registry). Data sharing will follow the policies of the Beijing Hospital Authority and the sponsor. Reasonable requests from researchers for data sharing will be considered, and anonymized data may be provided as appropriate, ensuring the confidentiality of participants' personal information.

Before any paper or report is published, no participant may disclose interim results or unpublished data without the sponsor's permission, to avoid misinterpretation of the findings. Published content will present aggregate data only, without revealing individual identities.