Pegargiminase (ADI-PEG20)

Pegargiminase (ADI-PEG 20) is an investigational enzyme therapy that depletes the amino acid arginine from the bloodstream, starving cancer cells that lack the enzyme argininosuccinate synthetase 1 (ASS1). Because ASS1-deficient cancer cells cannot manufacture their own arginine the way normal cells can, removing it from circulation selectively targets them. The drug has been studied specifically in malignant pleural mesothelioma and other ASS1-deficient cancers.

Origin

ADI-PEG-20 is built from the enzyme arginine deiminase (ADI), originally isolated from the bacterium Mycoplasma hominis. The enzyme is chemically linked to polyethylene glycol (PEG), a biocompatible polymer that shields it from the immune system, prolongs its activity in the body, and reduces allergic reactions. The "20" refers to the 20-kilodalton molecular weight of the PEG component. It was developed by Polaris Pharmaceuticals to exploit a metabolic vulnerability found in certain cancers.

Significance in Asbestos Context

ADI-PEG-20 matters to people with asbestos-related disease because it has been studied specifically for malignant pleural mesothelioma, the cancer most closely linked to asbestos exposure. Roughly half of mesotheliomas lack ASS1 expression and may therefore be vulnerable to arginine deprivation. The ATOMIC-meso phase 2/3 trial evaluated ADI-PEG-20 combined with standard pemetrexed and cisplatin chemotherapy in newly diagnosed, ASS1-deficient pleural mesothelioma patients and reported a modest survival benefit. Knowing your tumor's ASS1 status is essential because it determines whether arginine deprivation therapy is even an option. Ask your oncologist about immunohistochemical (IHC) testing of your biopsy tissue if it has not already been done. In a legal claim, defense attorneys sometimes point to emerging therapies like ADI-PEG-20 to argue that prognosis is improving and damages should be reduced; your legal team will likely respond that the drug is not FDA-approved, is not widely available, is not a cure, and that eligibility depends on biomarker testing many patients do not pass. Clinical trial participation also creates medical records, treatment timelines, and out-of-pocket costs (travel, lodging, lost wages, caregiving) that can be relevant to damages.

Example Sentence

After tumor biomarker testing revealed that his mesothelioma lacked ASS1 expression, the former shipyard insulator's oncologist discussed enrolling in a clinical trial combining ADI-PEG-20 with standard chemotherapy.

Related Terms

Mesothelioma, Argininosuccinate Synthetase 1 (ASS1), Pemetrexed, Cisplatin, Biomarker Testing, Clinical Trial, Sarcomatoid Mesothelioma, Biphasic Mesothelioma, ASS1

Notes

• Ask your oncologist to order immunohistochemical (IHC) testing of your tumor tissue for ASS1 expression. This single result determines whether arginine deprivation therapy is even on the table. If your biopsy was done at a community hospital, tissue blocks can be sent to a reference laboratory; keep a copy of the pathology report showing the ASS1 result.
• Search ClinicalTrials.gov for "ADI-PEG-20 mesothelioma" to see currently enrolling studies, and ask whether NCI-designated centers with mesothelioma programs (such as MD Anderson, Memorial Sloan Kettering, Brigham and Women's, or Moffitt) have open slots.
• Reported side effects include allergic reactions, fatigue, injection-site reactions, and metabolic changes such as altered blood sugar. Ask your oncologist to walk through the risk-benefit profile in light of your stage, performance status, and other treatments.
• Preserve all tumor tissue and pathology slides. If you transfer care, specifically request that tissue blocks be retained rather than discarded. They may be needed for future biomarker testing or as evidence in your case.
• If you are pursuing an asbestos lawsuit or trust claim, tell your legal team immediately about any trial discussions or enrollment. It affects life-care planning, deposition scheduling, and damages documentation.
• Keep a dedicated folder (paper or digital) for every trial-related expense: travel receipts, hotel bills, mileage, meals, lost wages, and caregiver costs. These may be recoverable as damages.