What is proven, what is observed, what is not yet known
Arginine deprivation is not a new idea. It has fifteen years of laboratory work, dozens of clinical trials and one positive Phase III behind it. Argeon is the newest enzyme built on that foundation. It has been given to more than 100 patients, and its documented record consists of five structured observations. This page separates what is proven from what is observed.
Fifteen years of arginine deprivation
The principle in patients
The ATOMIC-Meso trial randomised 249 patients with non-epithelioid pleural mesothelioma, a cancer with a five-year survival of about 8 %, to chemotherapy with or without ADI-PEG 20. Median survival rose from 7.7 to 9.3 months, and the share of patients alive at three years roughly tripled. Side effects added by the enzyme were mostly injection-site reactions and mild blood count changes.
Earlier Phase II trials with ADI-PEG 20 showed disease control in liver cancer, melanoma and acute myeloid leukaemia, with the same pattern: responses in ASS1-negative tumours, loss of effect once antibodies appeared. Pegzilarginase has completed Phase I and II work in solid tumours, alone and with chemotherapy and anti-PD-1 therapy, with a manageable safety profile.
Trials of arginine deprivation
| Enzyme | Tumour | Phase | Patients | Result |
|---|---|---|---|---|
| ADI-PEG 20 + chemotherapy | Pleural mesothelioma | III | 249 | Survival extended, 7.7 → 9.3 months median; three-year survival roughly tripled |
| ADI-PEG 20 alone | Hepatocellular carcinoma, second line | III | 635 | No survival benefit; antibodies and ASS1-positive tumours in the trial population |
| ADI-PEG 20 | Melanoma | II | ~40 | Disease control in ASS1-negative tumours |
| ADI-PEG 20 | Acute myeloid leukaemia | II | 43 | Responses in a relapsed, poor-risk population |
| ADI-PEG 20 + chemotherapy | Sarcoma, pancreatic, lung | I/II | various | Tolerable; activity signals supporting combination |
| Pegzilarginase | Solid tumours | I/II | various | Tolerable; programme later refocused on arginase-1 deficiency |
| Argeon | Various | individual treatment | 100+ (5 documented) | Falling tumour markers in four of five documented cases; no adverse events reported |
How Argeon differs
| ADI-PEG 20 (pegargiminase) | AEB1102 (pegzilarginase) | Argeon | |
|---|---|---|---|
| Origin | recombinant bacterial protein (Mycoplasma) | recombinant human arginase 1, PEGylated | recombinant mammalian arginase, albumin-binding domain |
| Reaction | arginine → citrulline | arginine → ornithine | arginine → ornithine |
| Sensitive tumours | ASS1-negative | ASS1- or OTC-negative | ASS1- or OTC-negative |
| Immunogenicity | high; antibodies after ~8 weeks, loss of effect | low | low (our laboratory data, not independently verified) |
| Half-life | short | short to intermediate | extended by albumin binding (our laboratory data) |
| Clinical status | Phase III (ATOMIC-Meso, positive) | EU approval in ARG1 deficiency 2023; oncology Phase I/II | preclinical; individual cases; no approval |
| Combinations studied | cisplatin, pemetrexed, docetaxel, temozolomide, azacitidine, venetoclax | chemotherapy, anti-PD-1 | cisplatin, gemcitabine, trastuzumab, anti-PD-1/PD-L1, radiotherapy (planned) |
Compiled from our laboratory documentation and published literature. As of October 2026.
Early observations with Argeon
More than 100 patients have received Argeon through the programme and its partner physicians. For five of them, laboratory values before and during treatment were recorded in a form we can show. No control group, partly alongside standard therapy, so effects cannot be attributed with certainty. No adverse events were reported in any of them.
Triple-negative breast cancer, stage IV
Woman, 50, metastatic. Seven weekly doses alongside chemotherapy, March to June 2025.
Chronic lymphocytic leukaemia, stage A
Man, 48. Five weekly doses, May to June 2025, no other treatment.
Lung cancer, stage IV, bone metastases
2024.
Breast cancer recurrence, stage IV
2024.
Colorectal cancer, stage III
2024.
Dose dates and raw data are available in the clinicians' section.
What we do not know
Every patient is told this before consent.
Literature
- Delage B. et al. Arginine deprivation and argininosuccinate synthetase expression in the treatment of cancer. Int J Cancer 2010;126:2762–2772.
- Szlosarek P.W. et al. Pegargiminase plus first-line chemotherapy in patients with nonepithelioid pleural mesothelioma: the ATOMIC-Meso randomized clinical trial. JAMA Oncol 2024;10:475–483.
- Changou C.A. et al. Arginine starvation-associated atypical cellular death involves mitochondrial dysfunction, nuclear DNA leakage, and chromatin autophagy. PNAS 2014;111:14147–14152.
- Cheng P.N.-M. et al. Mono-PEGylated thermostable Bacillus caldovelox arginase mutant (BCA-M-PEG20) induces apoptosis, autophagy, cell cycle arrest and growth inhibition in gastric cancer cells. 2022.
- Zhang Y. et al. Pegylated arginine deiminase drives arginine turnover and systemic autophagy to dictate energy metabolism. Cell Rep Med 2022;3:100498.
- Tsai H.J. et al. A phase II study of arginine deiminase (ADI-PEG 20) in relapsed/refractory or poor-risk acute myeloid leukemia patients. Sci Rep 2017;7:11253.
- Zou S. et al. Arginine metabolism and deprivation in cancer therapy. Biomed Pharmacother 2019;118:109210.
- Dillon B.J. et al. Incidence and distribution of argininosuccinate synthetase deficiency in human cancers. Cancer 2004;100:826–833.
- European Medicines Agency. Loargys (pegzilarginase), EPAR, 2023.
Laboratory documentation on Argeon is available to clinicians on request.