PPAT phosphoribosyl pyrophosphate amidotransferase
ENSG00000128059 · protein coding · Open Targets profile
Catalyzes the formation of phosphoribosylamine from phosphoribosylpyrophosphate (PRPP) and glutamine. .
Each band is a group of drugs. It runs from the kind of drug on the left to the furthest stage that drug has reached in any disease on the right. Thicker bands mean more drugs.
Approved bands are highlighted. Withdrawn means the drug was pulled from the market or from development. A combined phase counts as the later one (Phase 1/2 is shown as Phase 2). Hover a band for the drug names. Source: Open Targets Platform, fetched live.
Each row is a cancer, strongest overall evidence first. The two dots show how strong the inherited (germline) and tumour-mutation (somatic) evidence is; the line between them is the gap.
Scores run from 0 (no evidence) to 1 (strongest). A missing dot at 0 means Open Targets holds no evidence of that kind. Source: Open Targets Platform, fetched live.
Tractability
- Small molecule
- Approved Drug, Druggable Family
- PROTAC
- Database Ubiquitination, Half-life Data
gnomAD loss of function constraint: o/e 0.3324500024318695 (upper bound 0.4830799996852875). Low values mean loss of function is poorly tolerated, a safety flag for inhibition.
Who runs trials of these drugs
Principal investigators and study chairs on 175 registry trials, updated in the last three years, of the most advanced drugs against PPAT (azathioprine, mercaptopurine), ranked by Phase 2+ trials. Live from ClinicalTrials.gov.
- Elias JabbourM.D. Anderson Cancer Center · 3 of 3 trials Phase 2+
- Jianxiang WangInstitute of Hematology & Blood Diseases Hospital, China · 3 of 3 trials Phase 2+
- Loic GUILLEVINAssistance Publique - Hôpitaux de Paris · 3 of 3 trials Phase 2+
- Xiaofan ZhuInstitute of Hematology and Blood Diseases Hospital, CAMS & PUMC · 3 of 3 trials Phase 2+
- Wendy StockUniversity of Chicago · 2 of 3 trials Phase 2+
- Akshay SharmaSt. Jude Children's Research Hospital · 2 of 2 trials Phase 2+
- Benjamin TerrierAP-HP - Service médecine interne · 2 of 2 trials Phase 2+
- Ibrahim AldossCity of Hope Medical Center · 2 of 2 trials Phase 2+
- Paola CastellaniZambon SpA, Chief Medical Officer and R&D · 2 of 2 trials Phase 2+
- Seth E. KarolSt. Jude Children's Research Hospital · 2 of 2 trials Phase 2+
- Yi-Jin GaoShanghai Children's Medical Center · 2 of 2 trials Phase 2+
- Smita BhatiaChildren's Oncology Group · 1 of 2 trials Phase 2+
- Agata TymińskaMedical University of Warsaw · 1 of 1 trials Phase 2+
- Albert AssadIncyte Corporation · 1 of 1 trials Phase 2+
- Alberto Sanchez-FueyoKing's College London · 1 of 1 trials Phase 2+
Registry trials of azathioprine, mercaptopurine updated in the last three years, counted by the country group of their listed sites. A trial with sites in several groups counts in each; 113 of 160 have all sites in one country.
Site counts are not patients per country, and trials registered only outside ClinicalTrials.gov are not covered. Where sites are is a fact about the record, not a judgement of its quality. Europe is the EU and EEA, the UK and Switzerland. 15 trials list no sites and are left out. Source: ClinicalTrials.gov, fetched live.
69 trials of drugs against PPAT were stopped early; 7 give no reason
Terminated, withdrawn and suspended interventional trials of azathioprine, mercaptopurine, newest update first, live from ClinicalTrials.gov. Each reason is quoted exactly as the registry gives it; we do not sort reasons into safety, efficacy or business. Dates are the last registry update. Showing the 25 most recent of 69.
- withdrawn · 2026-10-15 · Brigham and Women's Hospital · matched by the registry's drug synonyms“Attempts to renew our protocol have not been accepted. Also, composition of the team and institutional goals have changed.”
- suspended · 2026-10-05 · Children's Oncology Group · Mercaptopurine“All potential pilot phase pts have been enrolled.”
- terminated · 2026-07-30 · M.D. Anderson Cancer Center · Mercaptopurine“the study was closed early due to competing trials”
- terminated · 2025-11-10 · University of Southern California · Azathioprine“Research contract expired”
- terminated · 2025-08-11 · M.D. Anderson Cancer Center · Mercaptopurine“The study was terminated early due to slow enrollment.”
- terminated · 2025-06-08 · M.D. Anderson Cancer Center · Mercaptopurine“Study was closed early due to low accrual and lack of response.”
- terminated · 2025-03-14 · Charite University, Berlin, Germany · Azathioprine“Insufficient patient recruitment”
- terminated · 2025-02-21 · Boston Medical Center · matched by the registry's drug synonyms“Unable to recruit adequate numbers of participants to answer the research question.”
- terminated · 2025-01-22 · Washington University School of Medicine · matched by the registry's drug synonyms“poor recruitment during pandemic and after”
- withdrawn · 2024-05-17 · National Cancer Institute (NCI) · Mercaptopurine“Other - Protocol moved to Disapproved”
- terminated · 2024-04-05 · Gilead Sciences · matched by the registry's drug synonyms“Sponsor decision to terminate study.”
- terminated · 2024-03-07 · King's College London · Tacrolimus, cyclosporine and/or mycophenolic acid, mycophenolate mofetil or azathioprine“Primary endpoint not reached.”
- withdrawn · 2024-02-22 · University of Michigan Rogel Cancer Center · matched by the registry's drug synonyms“The PI plans to revise the study design in a new protocol”
- terminated · 2023-11-07 · Washington University School of Medicine · Azathioprine“Sponsor”
- withdrawn · 2023-08-03 · University of New Mexico · matched by the registry's drug synonyms“This is a duplicate record and the sponsor has registered the study.”
- terminated · 2022-11-04 · M.D. Anderson Cancer Center · Mercaptopurine“Due to Competing Studies”
- withdrawn · 2022-05-04 · Brigham and Women's Hospital · matched by the registry's drug synonyms“Decline in COVID cases”
- terminated · 2022-05-02 · University of California, San Diego · matched by the registry's drug synonyms“Original investigator for the trial has left”
- terminated · 2022-03-14 · Chinese SLE Treatment And Research Group · Azathioprine“Because of insufficient enrollement”
- withdrawn · 2021-03-18 · Shaare Zedek Medical Center · Azathioprine“No Participants Enrolled”
- terminated · 2021-03-17 · Therapeutic Advances in Childhood Leukemia Consortium · matched by the registry's drug synonyms“The study was stopped due to poor accrual and lack of funding.”
- terminated · 2020-12-22 · Genentech, Inc. · Azathioprine“Study was terminated due to an imbalance of serious and opportunistic infections in the ocrelizumab treated patients versus the placebo arm.”
- terminated · 2020-09-17 · Genentech, Inc. · Immunosuppressive regime (azathioprine, mycophenolate mofetil or methotrexate)“The study was terminated prematurely when the decision was made that ocrelizumab was not likely to benefit this patient population.”
- terminated · 2020-03-17 · Asahi Kasei Therapeutics, Inc. · Azathioprine“Study was discontinued due to slow enrollment”
- withdrawn · 2020-03-10 · Medical College of Wisconsin · Rituximab (RTX) and Azathioprine (AZA)“No funding for study.”
Paediatric incentives and obligations for PPAT's drugs
For azathioprine, mercaptopurine: what EMA and FDA publish about paediatric plans, orphan status and pediatric approvals, and how many registered studies take children. Each line is a yes, no or not published fact from the record linked under it; none of it is a forecast.
- FDA pediatric target list: no · PPAT is not on the listRule: Target is on FDA's Pediatric Molecular Target List (relevant targets). Source: FDA Pediatric Molecular Target List (Listed as February 2026 on the FDA Pediatric Oncology page; the file served is 9.7.22_the_relevant_molecular_target_list.xlsx, whose Summary of Changes sheet is headed 'SEPTEMBER 2022 UPDATE' (footnote date 2022-09-01)), 2026-11-11
- EU paediatric investigation plan: no · No EMA paediatric investigation plan decision names azathioprine, mercaptopurineRule: An EMA PIP decision (agreement, modification or waiver) lists the drug as its active substance, exact name. Source: EMA data download (dated snapshot), 2026-11-11
- EU orphan designation: yes · EU/3/09/628 expired 30 Apr 2009: Treatment of acute lymphoblastic leukaemia; EU/3/07/496 positive 22 Oct 2007: Treatment of acute lymphoblastic leukaemiaRule: An EU orphan designation lists the drug as its active substance (exact name) or belongs to a medicine that does; withdrawn and expired designations are listed with their status. Source: EMA data download (dated snapshot), 2026-11-11
- Authorised in the EU: yes · Jayempi: authorised since 21 Jun 2021; Xaluprine (previously Mercaptopurine Nova Laboratories): authorised since 9 Mar 2012; Loulla: application withdrawn, orphan medicineRule: An EMA medicine record lists the drug as its active substance or INN, exact name; national-only authorisations are not in this file. Source: EMA data download (dated snapshot), 2026-11-11
- FDA orphan designation: not published · FDA's orphan designation database turns away automated requests, so this app does not read it; search it by hand at the linkRule: Would be: an FDA orphan designation names the drug. Source: FDA orphan designations search
- FDA pediatric oncology approval: yes · Mercaptopurine [Purinethol tablet] &, 11 Sept 1953: Treatment of adult and pediatric patients with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimenRule: FDA's Pediatric Oncology Drug Approvals table names the drug. Source: FDA Pediatric Oncology Drug Approvals (content current as of 2026-03-03), 2026-11-12
- Registered studies open to children: yes · 225 interventional studies of azathioprine, mercaptopurine include patients under 18; 49 are recruiting, not yet recruiting or activeRule: The registry's age group includes Child (birth to 17 years), which also counts studies that set no minimum age. Source: ClinicalTrials.gov search, 2026-11-12
Rare pediatric disease voucher. FDA, content current as of 29 Apr 2026: “As of February 3, 2026, enactment of the Consolidated Appropriations Act, 2026, the rare pediatric disease PRV program will sunset after September 30, 2029. FDA may not award any PRVs under this program after September 30, 2029.” Voucher sale prices are not shown here; they appear only as company-reported news. FDA: Rare Pediatric Disease Designation and Priority Review Voucher Programs
All 3 drugs and clinical candidates as a table
Each drug, stage and indication links to its Open Targets record, where the trials and approvals behind it are listed. Salt forms (for example a mesylate) are listed as Open Targets records them, as separate entries.