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Hydroxyurea

Also known as Hydroxycarbamide, Hydrea, Droxia

An oral capsule generally described as an inhibitor of ribonucleotide reductase, which slows DNA synthesis. The 2025 US Hydrea label lists resistant chronic myeloid leukaemia and, with chemoradiation, locally advanced head and neck squamous cell carcinoma.

From discovery to approval

  1. 1963 · Earliest report found

    Stearns, Losee and Bernstein's 1963 paper is titled 'Hydroxyurea. A new type of potential antitumor agent'. A 2021 review says the compound's biological impact has been known for almost a century and its antitumour abilities were first reported in the 1960s, citing that paper and a 1965 study of congeners against leukaemia L1210.[2][3][4][5]

  2. 1967-12-07 · FDA regular

    Original approval, classed as a Type 1 new molecular entity with priority review in the Drugs@FDA history. The 1967 label and letter are not available there, so the original indication is not stated here (the 2025 label lists resistant chronic myeloid leukaemia and locally advanced head and neck squamous cell carcinoma with chemoradiation). The type regular is an inference: no accelerated-approval wording was found.[6]

How it works

The Hydrea label says its precise antineoplastic mechanism cannot be described, but studies support the hypothesis that it inhibits DNA synthesis as a ribonucleotide reductase inhibitor, without affecting RNA or protein synthesis. A 2021 review says it arrests cells in S phase.[1]

Where it came from and why

No source read says why hydroxyurea was tested against cancer. Young and Hodas (1964) reported that it inhibited incorporation of thymidine into the DNA of HeLa cells without affecting RNA or protein precursors, and the title of a 1968 report identifies inhibition of ribonucleoside diphosphate reductase.

Cancers

  • Chronic myeloid leukaemia

    The 2025 Hydrea label lists treatment of resistant chronic myeloid leukaemia.[1]

  • Chronic myeloid leukaemia: comparison with busulfan

    A 1993 randomised comparison by the German CML Study Group is titled as showing prolongation of survival by hydroxyurea compared with busulfan.[7]

  • Chronic myeloid leukaemia (early clinical report)

    A 1965 paper by Kennedy and Yarbro is titled as describing metabolic and therapeutic effects of hydroxyurea in chronic myelogenous leukaemia (title only).[8]

  • Head and neck cancer

    The 2025 Hydrea label lists locally advanced squamous cell carcinomas of the head and neck, excluding the lip, in combination with concurrent chemoradiation.[1]

  • Cervical cancer

    The Gynecologic Oncology Group trial GOG-85, titled as a randomised comparison of fluorouracil plus cisplatin versus hydroxyurea as an adjunct to radiation therapy in stage IIB-IVA carcinoma of the cervix.[9]

Worth knowing

  • A 2021 review notes that hydroxyurea's reversible inhibition of DNA replication makes it a common laboratory reagent for synchronising cell cycles.[3]
  • The same review describes hydroxyurea as a staple agent in sickle anaemia therapy as well as an effective treatment for chronic myeloproliferative disorders; this profile covers its cancer use.[3]
  • The same review says it has been suggested that hydroxyurea facilitates skin cancer progression.[3]
  • Drugs@FDA lists the original Hydrea approval (NDA 016295) as 7 December 1967, a Type 1 new molecular entity with priority review; the 1967 label is not available there.[6]

On this site

References

  1. Waylis Therapeutics LLC. Hydrea (hydroxyurea capsules): prescribing information. DailyMed, set ID 8d41152f-a98a-4abc-afdf-a909012434a0, published 17 September 2025. Source
  2. STEARNS B, LOSEE KA, BERNSTEIN J. HYDROXYUREA. A NEW TYPE OF POTENTIAL ANTITUMOR AGENT. J Med Chem. 1963;6:201. PubMedDOI
  3. Musiałek MW, Rybaczek D. Hydroxyurea-The Good, the Bad and the Ugly. Genes (Basel). 2021;12(7). PubMedDOI
  4. YOUNG CW, HODAS S. HYDROXYUREA: INHIBITORY EFFECT ON DNA METABOLISM. Science. 1964;146(3648):1172-4. PubMedDOI
  5. Krakoff IH, Brown NC, Reichard P. Inhibition of ribonucleoside diphosphate reductase by hydroxyurea. Cancer Res. 1968;28(8):1559-65. PubMed
  6. U.S. Food and Drug Administration. Drugs@FDA: approval date(s) and history, letters, labels for NDA 016295 (Hydrea and Droxia, hydroxyurea). Page read 2026-10-29. Source
  7. Hehlmann R, Heimpel H, Hasford J, Kolb HJ, Pralle H, Hossfeld DK, et al. Randomized comparison of busulfan and hydroxyurea in chronic myelogenous leukemia: prolongation of survival by hydroxyurea. The German CML Study Group. Blood. 1993;82(2):398-407. PubMed
  8. Kennedy BJ, Yarbro JW. Metabolic and therapeutic effects of hydroxyurea in chronic myelogenous leukemia. Trans Assoc Am Physicians. 1965;78:391-9. PubMed
  9. Whitney CW, Sause W, Bundy BN, Malfetano JH, Hannigan EV, Fowler WC Jr, et al. Randomized comparison of fluorouracil plus cisplatin versus hydroxyurea as an adjunct to radiation therapy in stage IIB-IVA carcinoma of the cervix with negative para-aortic lymph nodes: a Gynecologic Oncology Group and Southwest Oncology Group study. J Clin Oncol. 1999;17(5):1339-48. PubMedDOI