Thymopentin: Promising Immunomodulator

Thymopentin, also known as TP-5, is a synthesized derivative of thymopoietin, a naturally occurring hormone responsible for inducing T-cell precursors to differentiate and mature. A study at the Istituto di Patologia Medica in Bari, Italy, reported thymopentin-related increases in T4 cells and some improvement in symptoms for 21 people. Two studies of thymopentin published at the Sixth International Conference on AIDS pointed to stabilization of T-helper counts and p24 antigenemia in asymptomatic and mildly symptomatic patients during treatment with thymopentin. One of the studies was too small to see differences in disease progression. In the larger study, none of the treated patients progressed to symptoms, compared to four of the placebo patients who did progress. No side effects were attributed to thymopentin (Abstracts #S. B. 484 and S. B. 485).

We spoke to Kathy Labriola, L. V. N., who managed a third thymopentin trial for Marcus Conant, M. D., a well-known San Francisco physician and researcher. Ms. Labriola shared the preliminary results of this trial, which was concluded last July but has not yet finished a statistical analysis. The study enrolled 100 asymptomatic participants and lasted one year. No other HIV drugs were used, except that for six months of the study, ten people were taking AZT. Participants receiving active drug were given 50 mg once a week. (In the previous studies of thymopentin, the same dose was given three times a week.)

When the trends of symptom development were identified, thymopentin clearly showed some protective benefits. Of those participants getting a placebo, 21 developed some observable symptoms, compared to only 13 receiving thymopentin. Nobody who received the drug in the study progressed to AIDS, but two who were in the placebo group did. In addition, four in the placebo group developed serious cases of herpes zoster, or shingles, two experienced outbreaks of genital warts, and eight were troubled by fungal skin infections. In the treatment group, four people noticed skin infections, but none experienced shingles or warts.

Serologic markers were not as descriptive. The placebo group experienced a slightly sharper decline in average T4-helper cell counts, and the ratio of T4 to T8 cells, than did the treatment group. However, two participants receiving thymopentin became mildly positive for p24 antigenemia, while everyone on placebo remained antigen-negative.

Dr. Conant is now recruiting for a trial of thymopentin combined with AZT. The number for more information is 415/923- 0555.

Several other thymus preparations have been under study in AIDS research as possible immunomodulators. These include thymosin, thymostimulin, thymomodulin, thymic humoral factor, calf thymus lysate, and thymus implants. We will report any significant news of these agents as they develop.

References

Thompson, S E and others. Effects of thymopentin on disease progression and surrogate markers in HIV infection-A one year study. Abstract #S. B. 484, Sixth International Conference on AIDS, San Francisco, June 20-24, 1990.

Conant, M and others. Twenty-four week double blind evaluation of thymopentin treatment on disease progression in HIV infected patients. Abstract # 485, Sixth International Conference on AIDS, San Francisco, June 20, 1990.