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Buphenyl (NaPBA)
Buphenyl (NaPBA) is a Nitrogen scavenger Small molecule drug developed by Amgen. It is currently in Phase 3 development for Urea cycle disorders (hyperammonemia management). Also known as: sodium phenylbutyrate.
Buphenyl (sodium phenylbutyrate) provides an alternative pathway for nitrogen excretion by conjugating with glutamine to form phenylacetylglutamine, which is then renally eliminated.
Buphenyl (NaPBA) is a small molecule used to treat various conditions, including Urea Cycle Disorders, Hepatic Encephalopathy, and Argininosuccinic Aciduria, as well as other inborn errors of amino acid metabolism. It is administered as an intervention in clinical trials, often in combination with other treatments.
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Baseline phase 3 → approval rate
+58.3pp
Industry-wide phase 3 drugs reach approval ~58.3% of the time (BIO/Informa 2023 industry benchmark across all therapeutic areas). -
Rare-disease pathway favourability
+5.0pp
Rare-disease drugs benefit from FDA Orphan Drug Act, smaller pivotal trials, and more flexible endpoints. Approval rates run ~5pp above baseline. -
Big-pharma sponsor
+3.0pp
Amgen is a top-20 pharma sponsor — historical approval rates run ~3pp above average due to scale, regulatory experience, and trial-design quality.
| Regulator | Country | Likely year | Lag vs FDA |
|---|---|---|---|
| FDA | US | 2028–2030 | — |
| EMA | EU | 2029–2031 | +0.7 yr |
| MHRA | GB | 2029–2031 | +0.7 yr |
| Health Canada | CA | 2029–2032 | +0.9 yr |
| TGA | AU | 2029–2032 | +1.2 yr |
| PMDA | JP | 2029–2032 | +1.5 yr |
| NMPA | CN | 2030–2033 | +2.3 yr |
| MFDS | KR | 2029–2032 | +1.4 yr |
| CDSCO | IN | 2029–2033 | +1.8 yr |
| ANVISA | BR | 2030–2033 | +2.3 yr |
Hover any row for the lag rationale. Lag estimates are reduced when the drug has FDA Breakthrough or EMA PRIME designation (sponsors file globally in parallel).
Estimate based on the BIO/Informa industry phase transition rates plus per-drug modifiers for therapeutic area, sponsor type, FDA designations, mechanism, and trial design. Per-jurisdiction lags from Tufts CSDD international approval studies. Not investment, clinical or regulatory advice. Methodology: /methodology#likelihood.
At a glance
| Generic name | Buphenyl (NaPBA) |
|---|---|
| Also known as | sodium phenylbutyrate |
| Sponsor | Amgen |
| Drug class | Nitrogen scavenger |
| Modality | Small molecule |
| Therapeutic area | Metabolic/Genetic Disorders |
| Phase | Phase 3 |
Mechanism of action
In urea cycle disorders, ammonia accumulates due to enzymatic defects in the urea cycle. Buphenyl bypasses the defective urea cycle by providing a nitrogen-scavenging mechanism: phenylbutyrate is metabolized to phenylacetate, which conjugates with glutamine via phenylacetyl-CoA:glutamine-N-acetyltransferase to form phenylacetylglutamine. This water-soluble conjugate is readily excreted in urine, effectively removing two nitrogen atoms per molecule of phenylacetylglutamine and reducing ammonia levels.
Approved indications
- Urea cycle disorders (hyperammonemia management)
Common side effects
- Nausea
- Vomiting
- Abdominal pain
- Taste aversion
- Hyperchloremic metabolic acidosis
Key clinical trials
- To Evaluate the Safety of Long-term Use of HPN-100 in the Management of Urea Cycle Disorders (UCDs) (PHASE4)
- Study of the Safety, Pharmacokinetics and Efficacy of HPN-100, in Pediatric Subjects With Urea Cycle Disorders (UCDs) (PHASE3)
- Study of the Safety and Tolerability of HPN-100 Compared to Sodium Phenylbutyrate in Children With Urea Cycle Disorders (PHASE2)
- Dose-Escalation Safety Study of HPN-100 to Treat Urea Cycle Disorders (PHASE2)
- Study of the Safety of HPN (Hyperion)-100 for the Long-Term Treatment of Urea Cycle Disorders (Treat UCD) (PHASE3)
- Efficacy and Safety of HPN-100 for the Treatment of Adults With Urea Cycle Disorders (PHASE3)
- Study of Glycerol Phenylbutyrate & Sodium Phenylbutyrate in Phenylbutyrate Naïve Patients With Urea Cycle Disorders (UCDs) (PHASE4)
- A Study of Glyceryl Tri-(4-phenylbutyrate) Administered Orally as a Single Dose, and Twice Daily for Seven Consecutive Days to Subjects With Hepatic Impairment With Cirrhosis and to a Control Group (PHASE1)
Primary sources
Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.
| Source | Used for |
|---|---|
| ClinicalTrials.gov | Trial enrolment, design, endpoints, results |
Competitive intelligence
For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:
- Buphenyl (NaPBA) CI brief — competitive landscape report
- Buphenyl (NaPBA) updates RSS · CI watch RSS
- Amgen portfolio CI
Frequently asked questions about Buphenyl (NaPBA)
What is Buphenyl (NaPBA)?
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What is Buphenyl (NaPBA) used for?
Who makes Buphenyl (NaPBA)?
Is Buphenyl (NaPBA) also known as anything else?
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Related
- Drug class: All Nitrogen scavenger drugs
- Manufacturer: Amgen — full pipeline
- Therapeutic area: All drugs in Metabolic/Genetic Disorders
- Indication: Drugs for Urea cycle disorders (hyperammonemia management)
- Also known as: sodium phenylbutyrate
Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing