Off-label drugs for cancer

Off-label drugs are drugs that are used for a disease or condition other than the one they were originally approved for. For example, Metformin was originally approved to treat 2 diabetes but is also used off-label to treat cancer.

Here are some off-label drugs that have shown efficacy in cancer treatment.

Bisphosphonates (anti-hypercalcemia drugs)

This study involving 18 766 women with early breast cancer, says:
…When the study authors looked at the findings according to the trial participants’ menopausal status, they found that treatment with adjuvant bisphosphonates had no effect on any of the outcomes for premenopausal women. However, among the 11,767 postmenopausal women included in the analysis, the use of bisphosphonates was associated with statistically significant reductions in distant recurrence, in bone recurrence, and in death from breast cancer.

Honokiol

This study says: Honokiol, a natural biphenolic compound, exerts anticancer effects through a variety of mechanisms on multiple types of cancer with relatively low toxicity…Additionally, honokiol inhibited the migration and invasion of ovarian cancer cells.

This study says:
Here…we report that HNK exerts inhibitory effects on the metastasis of lung cancer cells to the brain.

This study concluded:
Honokiol treatment induced growth inhibition of osteosarcoma cancer cells in vitro and in vivo.

This study says:
We have demonstrated for the first time that honokiol has potent anti-angiogenic and anti-tumor properties in vitro and is systemically active against aggressive angiosarcoma in vivo.

This study says: Mito-HNK potently inhibits orthotopic lung tumor growth as well as lung cancer metastasis to the brain…The low toxicity of Mito-HNK, coupled with its ability to cross the BBB [blood-brain barrier], makes it a highly attractive preventive and therapeutic agent for lung cancer and its brain metastases.

Niclosamide

Niclosamide belongs to the family of medicines called anthelmintics. Anthelmintics are medicines used in the treatment of worm infections.

Study: In conclusion, the present study offered new ideas for the treatment of chemoresistant HER2-positive breast cancer…Niclosamide combined with cisplatin may be considered as a novel treatment therapy for chemoresistant HER2-positive breast cancer.

Niclosamide, has been repurposed for cancer treatment due to its ability to disrupt multiple oncogenic signaling networks, such as Wnt/β-catenin, NF-κB and STAT3, all of which has fundamental roles in the survival, proliferation, and invasiveness and metastasis of tumors. (study)

Therefore, niclosamide holds great potential for the treatment of cancers and our present study provides strong support for its use in the treatment of TNBC. (study).

Mifepristone

This study of 34 ovarian cancer patients treated with Mifepristone says: Nine (26.5%) of these patients had a response to Mifepristone. Three (9%) patients had a complete response, and six (17.5%), a partial response…Laboratory studies show thatMifepristone can target cancer stem cells. Conclusion: Mifepristone has activity against ovarian cancer resistant to cisplatin and paclitaxel. The drug is well tolerated.

Case Report: We show long-term high-quality survivalfollowing single-agent treatment with a progesterone receptor antagonist in two cases of advanced metastatic cancer.

This study says: In summary, we have shown that mifepristone is a potent blocker of ovarian cancer growth in vitro and in vivo. The feasibility of using mifepristone to enhance the efficacy of conventional chemotherapy for ovarian cancer is encouraging and requires further investigation.

Case Report: We show long-term high-quality survival following single-agent treatment with a progesterone receptor antagonist in two cases of advanced metastatic cancer. The US Food and Drug Association granted a compassionate-use investigational new drug approval for use of single-agent 200 mg mifepristone orally/day to a moribund woman with never-treated metastatic lung cancer and a male with bilateral renal cell carcinoma who had undergone only a unilateral hemi-nephrectomy. Both had long-term high-quality survival (5 years for the patient with lung cancer with complete remission of all lung lesions, and 12 years for the male patient with kidney cancer). Neither patient had any side-effects from mifepristone therapy. Conclusion: These cases helped influence the US Food and Drug Association in granting an investigator-initiated investigational new drug study on advanced non-small cell lung cancer.

Nitazoxanide (NTZ) – anti-parasite drug,

Source: Labiotech.eu
A widely used anti-parasite drug, nitazoxanide (NTZ), is able to break down a protein called beta-catenin, which is found at high levels in prostate and colon cancer cells and supports their growth and survival. This opens up the possibility of repurposing the drug for the treatment of these cancers.

This 2023 study concluded:
NTZ is a potential therapeutic agent for bone metastasis induced by the TGF-β/Ac-KLF5 signaling axis in prostate cancer and likely other cancers.

Tadalafil (drug used to treat erectile dysfunction)

This study involving 32 patients with Head and Neck Squamous Cell Carcinoma concluded: These findings demonstrate that tadalafil augments general and tumor-specific immunity in patients with HNSCC and has therapeutic potential in HNSCC. Evasion of immune surveillance and suppression of systemic and tumor-specific immunity is a significant feature of head and neck cancer development. This study demonstrates that a PDE5 inhibitor, tadalafil, can reverse tumor-specific immune suppression in patients with head and neck cancer, with potential for therapeutic application.

Page updated February 2026