Last updated: September 1, 2026
Plazomicin sulfate, marketed in the United States as Zemdri, failed commercially despite FDA approval for complicated urinary tract infections caused by susceptible gram-negative bacteria. Achaogen launched the drug in 2018 but entered bankruptcy less than one year later. Cipla acquired plazomicin-related assets in 2019, but the product did not develop into a material commercial franchise. The main causes were a narrow label, antimicrobial-stewardship restrictions, hospital procurement barriers, weak reimbursement economics, and competition from established generic antibiotics.
What is the FDA status of plazomicin sulfate?
The FDA approved Zemdri on June 25, 2018, for adults with complicated urinary tract infections, including pyelonephritis, caused by susceptible Enterobacteriaceae when alternative treatment options were limited or unavailable (U.S. Food and Drug Administration [FDA], 2018).
| Attribute |
Plazomicin sulfate |
| Brand name |
Zemdri |
| Active ingredient |
Plazomicin sulfate |
| Sponsor at approval |
Achaogen, Inc. |
| FDA approval date |
June 25, 2018 |
| Dosage form |
Intravenous injection |
| Approved indication |
Complicated urinary tract infections and pyelonephritis |
| Target pathogens |
Susceptible Enterobacteriaceae |
| Administration |
Once daily intravenous dosing |
| FDA review pathway |
Qualified Infectious Disease Product and priority review |
| Current U.S. commercial position |
No meaningful active commercial presence |
| Primary commercial holder after bankruptcy |
Cipla-related asset acquisition |
The FDA approval was based on the EPIC clinical trial, which compared plazomicin with meropenem in complicated urinary tract infections. The drug demonstrated noninferiority on the trial’s composite endpoint, but the clinical and commercial positioning remained narrow (FDA, 2018).
Plazomicin was not approved for bloodstream infections, hospital-acquired pneumonia, or ventilator-associated pneumonia. Its label also carried warnings for nephrotoxicity, ototoxicity, neuromuscular blockade, and fetal harm. Those risks were commercially important because aminoglycosides already had a reputation for renal and auditory toxicity.
When did plazomicin lose commercial exclusivity?
Plazomicin did not lose commercial exclusivity through a successful generic launch. Its commercial failure occurred before the product could establish a durable hospital market.
Achaogen launched Zemdri in the third quarter of 2018. In April 2019, the company filed for Chapter 11 bankruptcy after failing to obtain sufficient financing and commercial traction. Achaogen’s assets were subsequently sold, with Cipla acquiring rights associated with plazomicin and other assets for approximately $4.65 million (Achaogen, 2019; Cipla, 2019).
The key dates are:
| Date |
Event |
| June 25, 2018 |
FDA approved Zemdri |
| Q3 2018 |
U.S. commercial launch |
| April 2019 |
Achaogen filed for Chapter 11 bankruptcy |
| 2019 |
Cipla acquired plazomicin-related assets |
| After 2019 |
No sustained U.S. commercial growth |
| Current position |
Product has limited or no material U.S. market activity |
The relevant commercial issue was not simply patent expiry. Achaogen could not generate enough revenue to support manufacturing, field promotion, payer contracting, medical affairs, and post-launch development.
How large was the plazomicin market?
The addressable market was materially smaller than the epidemiology of drug-resistant infections suggested.
Plazomicin targeted multidrug-resistant gram-negative infections, including organisms resistant to other aminoglycosides. That population had high clinical need, but the drug was reserved for situations in which alternatives were limited. Hospitals typically use reserve antibiotics selectively, which restricts volume.
The market had four structural constraints:
- Low treatment frequency. Plazomicin was administered for serious infections but was not a routine first-line antibiotic.
- Hospital formulary controls. Antimicrobial stewardship programs limited use of new reserve antibiotics.
- Generic competition. Meropenem, amikacin, gentamicin, tobramycin, and colistin were available at substantially lower prices.
- Narrow regulatory labeling. The absence of broad approvals in pneumonia and bloodstream infection limited utilization.
The product’s once-daily intravenous dosing was operationally attractive, but that advantage did not overcome the cost and toxicity profile. Hospitals could use older generic aminoglycosides or newer reserve agents such as ceftazidime-avibactam, meropenem-vaborbactam, and cefiderocol depending on resistance mechanisms and local formularies.
What were Achaogen’s financial results after the Zemdri launch?
Achaogen’s financial trajectory deteriorated immediately after approval. The company had invested heavily in clinical development and regulatory preparation but generated only limited revenue after launch.
Achaogen reported approximately $0.1 million in Zemdri product revenue during 2018, according to its public filings. That amount was immaterial relative to the company’s research, selling, general and administrative expenses. The commercial launch therefore did not materially reduce cash burn (Achaogen, 2019).
| Financial factor |
Effect on Achaogen |
| Pre-approval development spending |
Created a high fixed-cost base |
| Post-launch sales |
Too low to support operating expenses |
| Commercial infrastructure |
Required before demand was established |
| Hospital adoption |
Slow and restricted |
| Financing environment |
Insufficient to fund the launch period |
| Bankruptcy outcome |
Asset sale rather than operating recovery |
Achaogen’s business model depended on a rapid increase in sales of a premium hospital antibiotic. That increase did not occur. The company’s market capitalization, financing capacity, and strategic flexibility declined quickly after launch.
The financial outcome illustrates a recurring problem in antibacterial drug development: a product can address serious resistance threats while producing low revenue because stewardship programs intentionally suppress use.
Which companies challenged or competed with plazomicin sulfate?
No major Paragraph IV litigation or generic challenge became a defining feature of the plazomicin market. The competitive threat was primarily commercial and therapeutic rather than patent-litigation driven.
Established generic antibiotics
Plazomicin competed with:
- Amikacin
- Gentamicin
- Tobramycin
- Meropenem
- Colistin
These products had lower acquisition costs and extensive hospital familiarity. Their limitations included resistance, toxicity, dosing complexity, or reduced activity against particular organisms.
Newer branded antibiotics
The more direct branded competitors included:
| Drug |
Company associated with U.S. commercialization |
Primary competitive relevance |
| Avycaz, ceftazidime-avibactam |
Allergan, later AbbVie |
Broad utility against selected resistant gram-negative infections |
| Vabomere, meropenem-vaborbactam |
Melinta Therapeutics |
Activity against certain carbapenem-resistant organisms |
| Fetroja, cefiderocol |
Shionogi |
Treatment option for difficult-to-treat gram-negative infections |
| Xacduro, sulbactam-durlobactam |
Innoviva/Sunovion |
Hospital-acquired and ventilator-associated bacterial pneumonia |
These products had broader or more differentiated positioning in some hospital settings. Their commercial success was also limited by stewardship, but they benefited from indications and clinical niches that were more attractive than plazomicin’s original label.
What patent protections covered plazomicin sulfate?
Plazomicin was protected by composition-of-matter, pharmaceutical composition, and related patent families associated with Achaogen and predecessor research programs. The commercial estate was more important as a barrier to early generic entry than as a source of long-term value after the company’s bankruptcy.
The principal patent categories were:
| Patent category |
Commercial purpose |
| Plazomicin compound claims |
Protect the active aminoglycoside derivative |
| Salt and pharmaceutical composition claims |
Cover plazomicin sulfate and injectable formulations |
| Manufacturing and synthesis claims |
Protect production routes and intermediates |
| Treatment-method claims |
Cover use against resistant bacterial infections |
| Formulation claims |
Protect injectable presentations and stability characteristics |
Public FDA patent-listing records and patent databases should be reviewed for the live Orange Book status of each patent because listing status, patent-term adjustment, terminal disclaimers, and post-grant changes affect the effective generic-entry analysis. No widely reported U.S. Paragraph IV litigation materially delayed a plazomicin generic launch.
The IP estate also had limited commercial leverage because the product’s sales base collapsed before a challenger could create meaningful litigation value. A technically strong patent position cannot sustain a drug with low utilization and weak reimbursement.
What was the Orange Book status of Zemdri?
Zemdri was an FDA-approved prescription product with U.S. patent and regulatory records associated with Achaogen. Its commercial status changed after Achaogen’s bankruptcy and the transfer of assets.
The Orange Book distinguishes between approval status and marketing status. A product may remain approved while having no active commercial distribution. Zemdri’s post-bankruptcy position should therefore be assessed through three separate questions:
- Whether the NDA remained approved.
- Whether the product was listed as discontinued for commercial reasons.
- Whether any patents remained listed and unexpired.
The product’s withdrawal from active commercialization was not driven by an FDA finding that it lacked efficacy or had an unacceptable safety profile. The primary failure was commercial.
How did licensing and asset transfers affect plazomicin?
Achaogen’s bankruptcy converted plazomicin from a vertically managed commercial product into an acquired asset. Cipla’s purchase provided an opportunity to preserve the product, manufacturing rights, and regulatory infrastructure at a low acquisition price.
The transaction economics were unfavorable for Achaogen’s original investors. A product that had required substantial development spending was transferred for a small fraction of the company’s cumulative investment. The transaction also reflected the difficulty of valuing antibiotics on expected sales alone.
For Cipla, the acquisition offered:
- Access to a recently approved antibiotic.
- A differentiated product for resistant gram-negative infections.
- Potential geographic expansion.
- Regulatory and manufacturing assets acquired below development cost.
The transaction did not produce a visible U.S. commercial recovery. The core constraints remained: limited use, hospital budget pressure, generic competition, and aminoglycoside toxicity.
What manufacturing and geographic barriers affected the market?
Plazomicin required sterile injectable manufacturing and hospital distribution. That created higher operating complexity than an oral antibiotic. The product could not rely on retail pharmacy volume and required institutional procurement, cold-chain or controlled distribution processes, medical education, and infectious-disease specialist adoption.
Geographic expansion also faced limits:
- U.S. approval was narrow.
- European and other-market regulatory filings required additional investment.
- Hospitals outside the United States had strong generic antibiotic substitution.
- National procurement systems often favor low-cost antibiotics.
- Antimicrobial stewardship policies restrict reserve-agent volume.
The manufacturing IP may have protected production routes and intermediates, but the economic barrier was weaker once the product’s market value declined. Generic injectable manufacturers could assess whether a technically complex process was commercially worthwhile, while the brand lacked the sales base needed to support premium pricing.
What generic launch risks exist for plazomicin?
The near-term generic threat was less important than the risk of commercial abandonment. A generic company would face limited demand, hospital formulary barriers, and the cost of developing an injectable product.
Potential generic-entry scenarios include:
| Scenario |
Commercial effect |
| No generic launch |
Product remains approved but commercially inactive |
| Single generic entrant |
Low-volume institutional market with price erosion |
| Multiple injectable generics |
Rapid price decline and limited brand value |
| Repositioning for resistant infections |
Requires clinical evidence and stewardship adoption |
| Public-sector procurement |
Could create volume but at low pricing |
A generic launch would likely require a validated sterile manufacturing process, bioequivalence or applicable regulatory data, stability studies, and sufficient hospital demand. Patent expiry alone would not guarantee entry.
How strong is the plazomicin patent estate commercially?
The patent estate was technically relevant but commercially weak after Achaogen’s collapse.
| Strength factor |
Assessment |
| Novel active ingredient |
Potentially strong composition protection |
| Injectable formulation |
Moderate protection, depending on claim scope |
| Manufacturing know-how |
Potential barrier for complex synthesis and sterile production |
| Method-of-use claims |
Narrower value because of limited label |
| Patent litigation record |
No major public litigation defining market access |
| Revenue support |
Weak after launch failure |
| Generic deterrence |
Potentially meaningful, but insufficient to create franchise value |
The narrow clinical label reduced the value of method-of-use patents. The product could not capture broad anti-infective demand, and the presence of inexpensive alternatives constrained pricing.
What is the long-term commercial outlook for plazomicin sulfate?
Plazomicin’s long-term value is more likely to arise from strategic or public-health use than from conventional branded sales. The drug could retain relevance in selected infections caused by resistant Enterobacteriaceae, particularly where susceptibility testing confirms activity and other options are unsuitable.
The commercial outlook remains constrained by:
- Limited approved use.
- Nephrotoxicity and ototoxicity concerns.
- Intravenous administration.
- Low routine hospital utilization.
- Generic substitutes.
- Weak incentives for antibiotic investment.
- Lack of a large, durable commercial owner.
A revived strategy would require a clear resistance-driven niche, stronger hospital reimbursement, public-sector purchasing commitments, or a new clinical-development program supporting additional indications. Without those conditions, plazomicin is unlikely to become a material revenue product.
Key Takeaways
- Plazomicin sulfate was FDA approved as Zemdri in June 2018 for complicated urinary tract infections and pyelonephritis.
- Achaogen reported only about $0.1 million in 2018 Zemdri product revenue.
- Achaogen filed for bankruptcy in April 2019, less than one year after launch.
- Cipla acquired plazomicin-related assets for approximately $4.65 million.
- The main competitive threat came from generic aminoglycosides and newer reserve antibiotics, not Paragraph IV litigation.
- Patent protection covered the compound, sulfate salt, formulations, manufacturing, and treatment methods, but the estate did not generate durable commercial value.
- The drug’s failure resulted from low utilization, stewardship restrictions, toxicity concerns, hospital procurement barriers, and insufficient reimbursement.
- Any future value depends on targeted use against resistant gram-negative infections rather than broad antibiotic commercialization.
FAQs About Plazomicin Sulfate
Is plazomicin sulfate still marketed in the United States?
Plazomicin has no meaningful active U.S. commercial presence following Achaogen’s bankruptcy and the subsequent asset transfer to Cipla.
Did the FDA withdraw Zemdri for safety reasons?
The product’s commercial discontinuation followed business failure and weak sales. The principal event was not an FDA determination that the drug lacked efficacy.
Is plazomicin sulfate a generic antibiotic?
No. Plazomicin was developed and approved as a branded, novel aminoglycoside antibiotic. Its commercial product was Zemdri.
Why did hospitals use plazomicin infrequently?
Hospitals reserved it for selected resistant gram-negative infections because of its narrow label, intravenous administration, nephrotoxicity risk, and the availability of lower-cost alternatives.
Could plazomicin regain commercial value?
A recovery would require a defined clinical niche, additional evidence in resistant infections, reliable reimbursement, and a commercial or public-sector purchasing model that supports low-volume antibiotic use.
References
Achaogen, Inc. (2019). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. U.S. Securities and Exchange Commission.
Cipla Limited. (2019). Cipla acquires assets of Achaogen, including plazomicin. Cipla corporate announcement.
U.S. Food and Drug Administration. (2018). FDA approves new antibiotic for complicated urinary tract infections. FDA Drug Safety and Availability.
U.S. Food and Drug Administration. (2018). Zemdri (plazomicin sulfate) prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA Orange Book.
