Bestatin

Immune & Anti-Inflammatory

Also known as: Ubenimex, Ubex, Bestatin Hydrochloride, (2S,3R)-3-Amino-2-Hydroxy-4-Phenylbutanoyl-L-Leucine

Aminopeptidase InhibitorsResearch phase: Post-marketing (Japan), multiple clinical trialsRegulatory: Approved in Japan for AML adjuvant immunotherapy (since 1987). Not FDA-approved. Studied in multiple trials for solid tumors, renal cell carcinoma, and pulmonary arterial hypertension. Available as research compound internationally.

Mechanism

Bestatin (also known as Ubenimex) is a dipeptide that boosts immune function by blocking enzymes called aminopeptidases, which normally trim peptides on the surface of immune cells. By inhibiting these enzymes, Bestatin increases the activity of T-cells, B-cells, macrophages, and NK cells. It was originally approved in Japan for use alongside chemotherapy in acute myeloid leukemia (AML) to help restore immune function. It has also been studied for hypertension (it inhibits enzymes in the renin-angiotensin system) and as a potential anti-cancer agent on its own.

Technical detail

Bestatin/Ubenimex is a synthetic dipeptide analog isolated originally from Streptomyces olivoreticuli. Mechanism: competitive inhibitor of aminopeptidase N (CD13/APN), leucine aminopeptidase (LAP), and aminopeptidase B. CD13 is a zinc-dependent metalloprotease expressed on myeloid cells, endothelial cells, and various tumor cells. Inhibition of CD13: (1) enhances antigen processing and presentation, augmenting T-cell immune surveillance; (2) increases surface expression of enkephalins and other immunomodulatory peptides normally degraded by aminopeptidases; (3) reduces tumor angiogenesis (CD13 promotes endothelial tube formation); (4) directly inhibits leukemic cell proliferation. Also inhibits leukotriene A4 hydrolase (LTA4H), reducing LTB4-driven inflammation. In RCTs: improved 5-year survival in AML when combined with chemotherapy (Japanese clinical data). Enhances NK cell cytotoxicity and macrophage tumoricidal activity.

Evidence

  • Clinical trials of bestatin for leukemia and solid tumors.

    Ota et al. (1992) — Biotherapy — PMID: 1599804

    Review of leukemia and solid-tumor studies reported prolonged remission or survival signals for bestatin in some hematologic malignancies and selected solid tumors, while emphasizing that adjuvant benefit required further confirmation.

    emerging

  • Bestatin in resected lung cancer. A randomized clinical trial.

    Yasumitsu et al. (1990) — Acta Oncologica — PMID: 2223157

    Randomized clinical trial in 153 patients found significantly prolonged survival with bestatin versus control in the squamous-cell lung cancer subgroup, with no significant benefit in adenocarcinoma.

    moderate

  • Double-blind trial of bestatin in HIV-positive patients.

    Hørding et al. (1990) — Biomedicine & Pharmacotherapy — PMID: 2081275

    In 22 HIV-positive men randomized to bestatin 60 mg/day or placebo for 4 weeks, bestatin did not improve immunological, hematological, biochemical, or clinical variables versus placebo.

    moderate
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