Last reviewed 2026-04-23 · How we verify

Nafcillin (or equivalent)

Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) · Phase 3 active Small molecule

Nafcillin (or equivalent) is a Beta-lactam antibiotic (semi-synthetic penicillin) Small molecule drug developed by Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA). It is currently in Phase 3 development for Serious infections caused by susceptible Staphylococcus aureus (including methicillin-susceptible strains), Bacterial endocarditis, Osteomyelitis.

Nafcillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins.

Nafcillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins. Used for Serious infections caused by susceptible Staphylococcus aureus (including methicillin-susceptible strains), Bacterial endocarditis, Osteomyelitis.

Likelihood of approval

63.3% vs 58.3% industry baseline

If approved by FDA: likely 2028–2030

Steps remaining: NDA/BLA submission

Confidence: High

Why this estimate

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).
Anti-infectives pathway favourability +2.0pp
Microbiological endpoints + non-inferiority designs raise approval rates above baseline.
Big-pharma sponsor +3.0pp
Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) is a top-20 pharma sponsor — historical approval rates run ~3pp above average due to scale, regulatory experience, and trial-design quality.

Predicted approval windows by jurisdiction (conditional on FDA approval)

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	Nafcillin (or equivalent)
Sponsor	Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)
Drug class	Beta-lactam antibiotic (semi-synthetic penicillin)
Target	Penicillin-binding proteins (PBPs)
Modality	Small molecule
Therapeutic area	Infectious Disease
Phase	Phase 3

Mechanism of action

Nafcillin is a semi-synthetic penicillin that works by disrupting the cross-linking of peptidoglycan in bacterial cell walls, leading to cell wall instability and bacterial death. It is particularly effective against beta-lactamase-producing Staphylococcus aureus, including methicillin-resistant strains in some cases, making it useful for serious gram-positive infections.

Approved indications

Serious infections caused by susceptible Staphylococcus aureus (including methicillin-susceptible strains)
Bacterial endocarditis
Osteomyelitis
Pneumonia

Common side effects

Hypersensitivity reactions (rash, urticaria)
Phlebitis at injection site
Diarrhea
Nausea
Anaphylaxis

Key clinical trials

Safety and Efficacy Study of Daptomycin Compared to Active Comparator in Pediatric Participants With Acute Hematogenous Osteomyelitis (AHO) (MK-3009-006) (PHASE3)

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:

Nafcillin (or equivalent) CI brief — competitive landscape report
Nafcillin (or equivalent) updates RSS · CI watch RSS
Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) portfolio CI

Frequently asked questions about Nafcillin (or equivalent)

What is Nafcillin (or equivalent)?

Nafcillin (or equivalent) is a Beta-lactam antibiotic (semi-synthetic penicillin) drug developed by Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA), indicated for Serious infections caused by susceptible Staphylococcus aureus (including methicillin-susceptible strains), Bacterial endocarditis, Osteomyelitis.

How does Nafcillin (or equivalent) work?

Nafcillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins.

What is Nafcillin (or equivalent) used for?

Nafcillin (or equivalent) is indicated for Serious infections caused by susceptible Staphylococcus aureus (including methicillin-susceptible strains), Bacterial endocarditis, Osteomyelitis, Pneumonia.

Who makes Nafcillin (or equivalent)?

Nafcillin (or equivalent) is developed by Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) (see full Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) pipeline at /company/cubist-pharmaceuticals-llc-a-subsidiary-of-merck-co-inc-rahway-new-jersey-usa).

What drug class is Nafcillin (or equivalent) in?

Nafcillin (or equivalent) belongs to the Beta-lactam antibiotic (semi-synthetic penicillin) class. See all Beta-lactam antibiotic (semi-synthetic penicillin) drugs at /class/beta-lactam-antibiotic-semi-synthetic-penicillin.

What development phase is Nafcillin (or equivalent) in?

Nafcillin (or equivalent) is in Phase 3.

What are the side effects of Nafcillin (or equivalent)?

Common side effects of Nafcillin (or equivalent) include Hypersensitivity reactions (rash, urticaria), Phlebitis at injection site, Diarrhea, Nausea, Anaphylaxis.

What does Nafcillin (or equivalent) target?

Nafcillin (or equivalent) targets Penicillin-binding proteins (PBPs) and is a Beta-lactam antibiotic (semi-synthetic penicillin).

Drug class: All Beta-lactam antibiotic (semi-synthetic penicillin) drugs
Target: All drugs targeting Penicillin-binding proteins (PBPs)
Manufacturer: Cubist Pharmaceuticals LLC, a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) — full pipeline
Therapeutic area: All drugs in Infectious Disease
Indication: Drugs for Serious infections caused by susceptible Staphylococcus aureus (including methicillin-susceptible strains)
Indication: Drugs for Bacterial endocarditis
Indication: Drugs for Osteomyelitis

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing