Why does it have a boxed warning?

High-dose IL-2 can cause capillary leak syndrome, in which fluid leaks from blood vessels, leading to dangerously low blood pressure and organ damage.

Where can it be given?

The boxed warning requires that high-dose aldesleukin be given only in a specialised inpatient setting with intensive monitoring and cardiopulmonary support available.

Why is it used despite its toxicity?

Because a minority of patients achieve durable, sometimes complete and long-lasting remissions, which historically was rare with other therapies for these cancers.

EMA-approved

Aldesleukin — Complete Research Guide (2026)

Last updated 2026-06-30

TL;DR

Aldesleukin is a peptide catalogued under Immune. Neutral reference entry; EU status: EU-approved prescription medicine.

What is Aldesleukin?

Aldesleukin is recombinant human interleukin-2 (IL-2), a cytokine protein (marketed as Proleukin) rather than a small peptide, used as high-dose immunotherapy. It is FDA-approved for metastatic renal cell carcinoma and metastatic melanoma, where high-dose regimens can yield durable complete responses in a minority of patients.

The evidence base is human and substantial, including prospective series and a randomised trial, but responses come at the cost of severe, potentially life-threatening toxicity.

How does Aldesleukin work?

Aldesleukin binds the interleukin-2 receptor on T cells and natural-killer cells, driving clonal expansion and activation of cytotoxic lymphocytes and lymphokine-activated killer cells.

This amplified antitumour immune response underlies its activity but also causes widespread immune-mediated vascular toxicity.

What does the research say about Aldesleukin?

High-dose IL-2 produced durable complete responses in a subset of patients with metastatic renal cell carcinoma on long-term follow-up. ^[1]
In metastatic melanoma, high-dose IL-2 achieved durable objective responses, including long-lasting complete remissions in some patients. ^[2]
A randomised trial found high-dose IL-2 produced a higher response rate than subcutaneous IL-2 plus interferon in metastatic renal cell carcinoma. ^[5]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

[1] Long-term response data for 255 patients with metastatic renal cell carcinoma treated with high-dose recombinant interleukin-2 therapy — Fyfe GA et al., Journal of Clinical Oncology 1996. (Pooled analysis of clinical trials (long-term follow-up))
[2] High-dose recombinant interleukin 2 therapy for patients with metastatic melanoma: analysis of 270 patients treated between 1985 and 1993 — Atkins MB et al., Journal of Clinical Oncology 1999. (Retrospective pooled analysis)
[3] Treatment of 283 consecutive patients with metastatic melanoma or renal cell cancer using high-dose bolus interleukin 2 — Rosenberg SA et al., JAMA 1994. (Prospective clinical series)
[4] High-dose interleukin-2 for the treatment of metastatic renal cell carcinoma: a retrospective analysis of response and survival in patients treated in the surgery branch at the National Cancer Institute between 1986 and 2006 — Klapper JA et al., Cancer 2008. (Retrospective cohort analysis)
[5] Randomized phase III trial of high-dose interleukin-2 versus subcutaneous interleukin-2 and interferon in patients with metastatic renal cell carcinoma — McDermott DF et al., Journal of Clinical Oncology 2005. (Randomised controlled trial (phase III))

Dosing context

This is not medical advice or a usage recommendation. Dosing figures are reported research context only, cited from the published literature.

The high-dose regimen has been given as short intravenous bolus infusions every eight hours in hospital cycles, with doses frequently held or stopped for toxicity such as hypotension or organ dysfunction.

This is background context only and not a dosing recommendation; aldesleukin can only be administered safely in a specialised inpatient setting under expert supervision.

Side effects & safety profile

Aldesleukin carries an FDA boxed warning for capillary leak syndrome, a shift of fluid into tissues that causes hypotension, reduced organ perfusion, and potentially fatal cardiac, pulmonary, renal, and neurological complications.

Because of this, the boxed warning restricts it to administration only in specialised inpatient settings staffed and equipped for intensive monitoring and cardiopulmonary support, under a physician experienced in cancer immunotherapy.

It is contraindicated in patients with significant cardiac or pulmonary dysfunction or organ transplants, and treatment demands strict patient selection and rigorous supportive care.

Stacking & combinations

It has been studied in defined oncology combinations and adoptive cell-therapy protocols, but combining it with unapproved research peptides is unsupported and dangerous given its capillary-leak toxicity.

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Frequently asked questions

It is recombinant interleukin-2, an immune-signalling cytokine protein (brand name Proleukin) used as high-dose immunotherapy for certain metastatic cancers.

References

[1] Long-term response data for 255 patients with metastatic renal cell carcinoma treated with high-dose recombinant interleukin-2 therapy — Fyfe GA et al., Journal of Clinical Oncology 1996. PMID: 8708739. View sourceStudy: Pooled analysis of clinical trials (long-term follow-up)A subset of metastatic renal cell carcinoma patients achieved durable complete responses lasting years after high-dose IL-2.
[2] High-dose recombinant interleukin 2 therapy for patients with metastatic melanoma: analysis of 270 patients treated between 1985 and 1993 — Atkins MB et al., Journal of Clinical Oncology 1999. PMID: 10561265. View sourceStudy: Retrospective pooled analysisHigh-dose IL-2 produced objective responses in metastatic melanoma, with durable complete responses in a small but meaningful fraction of patients.
[3] Treatment of 283 consecutive patients with metastatic melanoma or renal cell cancer using high-dose bolus interleukin 2 — Rosenberg SA et al., JAMA 1994. PMID: 8120958. View sourceStudy: Prospective clinical seriesHigh-dose bolus IL-2 produced durable tumour regressions in patients with metastatic melanoma and renal cell cancer.
[4] High-dose interleukin-2 for the treatment of metastatic renal cell carcinoma: a retrospective analysis of response and survival in patients treated in the surgery branch at the National Cancer Institute between 1986 and 2006 — Klapper JA et al., Cancer 2008. PMID: 18457330. View sourceStudy: Retrospective cohort analysisA 20-year single-centre experience confirmed durable responses and long-term survival in a minority of metastatic renal cell carcinoma patients given high-dose IL-2.
[5] Randomized phase III trial of high-dose interleukin-2 versus subcutaneous interleukin-2 and interferon in patients with metastatic renal cell carcinoma — McDermott DF et al., Journal of Clinical Oncology 2005. PMID: 15625368. View sourceStudy: Randomised controlled trial (phase III)High-dose intravenous IL-2 produced a higher response rate than subcutaneous IL-2 plus interferon, supporting high-dose therapy for selected patients.

This article is for educational and research purposes only. Peptides discussed here are not approved for human consumption by the FDA, EMA, or equivalent regulators outside of specific clinical contexts. Always consult a licensed medical professional before any therapeutic use.