The hepatitis B oligonucleotide is a clean illustration of a failure mode worth carrying.
Thirty-two healthy participants received single doses up to 480 mg and tolerated them well; the main complaint was injection site reaction. Eight patients with chronic hepatitis B then received the same class of drug, and four developed drug-induced liver injury serious enough to stop the programme.
The healthy liver and the chronically infected liver are not the same organ. One has normal regenerative reserve, no immune activation against hepatocytes, and no fibrosis; the other has all three. A drug metabolised or accumulated hepatically encounters a different tissue in each, and phase 1 in healthy volunteers is designed to characterise pharmacokinetics and gross toxicity, not to predict organ-specific injury in disease.
The habit: when reading a phase 1 safety claim, ask whether the volunteers had the organ pathology the drug targets. Where they did not — which is usual — that safety result constrains the dose range and tells you little about tolerability in patients. The first real safety signal arrives in the first patients, which is exactly what happened here.
- Ask whether phase 1 volunteers had the pathology the drug targets
- Healthy livers differ in reserve, immune activation and fibrosis
- Phase 1 characterises pharmacokinetics and dose range, not disease-specific injury
- Idiosyncratic injury is by definition not predicted by exposure
- The first meaningful safety data come from the first treated patients
The statistics, in plain English
Phase 1 trials in healthy volunteers are small by design and powered only to detect common, dose-related toxicity. Idiosyncratic injury is neither common nor reliably dose-related, so no feasible healthy-volunteer study would have found this. That is a limitation of the design rather than a failure of its conduct.
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