FTC is being studied in treatment for HIV and hepatitis B (HBV). 350 million people worldwide are HBV infected. RG Gish and others reported at ICAAC on this phase I/II study of safety, pharmacokinetics and activity. Five once-daily doses (25, 50, 100, 200, 300 mg) were sequentially evaluated for 8 weeks in patient groups of about 8 individuals. Patients were positive for HbsAg and HBV-DNA at baseline. As you can see in following data high viral burdens can be associated with HBV. As well, the assays to measure viral load are not as developed as those used with HIV. Baseline viral loads ranged from 8.6 log in the 25 mg dose arm (n=8), to 7.1 log in the 100 mg dose (n=11), 7.5 log in the 300 mg dose (n=9), 8.3 log in the 200 mg arm (n=80). Investigators reported that suppression of HBV-DNA depended on baseline viral load and assay sensitivity, in that higher viral load reductions were seen when baseline viral loads were higher. On day 57 HBV-DNA reached undetectable when assayed by the Digene Hybrid Capture Assay (LLD 145,000 copies/ml) at low and moderate baseline viral loads and showed a moderate effect at high baseline viral loads. With the Chiron Amplicor HBV Monitor Assay (LLD 400 copies/ml), median HBV reductions of 4.0 log were seen in the 200 mg dose and the 25 mg dose. Average ALT went down from about 100 at baseline to about 75. In the 100 mg dose about 2 log reduction was seen. The half-life of FTC ranged from 6 to 10 hours in plasma. The steady state plasma concentrations increased nearly dose proportionally over the 25 and 300 mg dose range. FTC was reported to be well tolerated with 11% reporting headache (grade 2-3).

The high viral burden in HBV may require combination therapy. 3TC is further along in development and is available but several other drugs including FTC and adefovir are further behind in development. Some doctors are postponing treatment presumably waiting for additional therapies. As success treating HIV is occurring additional concerns may emerge for people with HIV such as HBV or HCV.