12 September 2019 - - US-based drugmaker MicuRx Pharmaceuticals, Inc has received positive top-line results for study MRX4-201, a US Phase 2 randomised, double-blind clinical trial comparing contezolid acefosamil (MRX-4) with linezolid for the treatment of acute bacterial skin and skin structure infections (ABSSSI), the company said.

Contezolid acefosamil met all primary and secondary efficacy endpoints with a potentially improved hematologic safety profile.

The Phase 2 trial enrolled 196 ABSSSI patients in a 2: 1 ratio (contezolid acefosamil 131 subjects, linezolid 65 subjects) at 7 centers in the United States to evaluate the safety and efficacy of the intravenous and oral formulations of contezolid acefosamil for 10-14 days of therapy compared to linezolid.

Contezolid acefosamil subjects started with a loading dose of 1500 mg IV followed by twice daily 1000 mg IV doses with the option after at least 3 IV doses to switch to 1300 mg oral doses twice daily; linezolid subjects started with 600 mg IV twice daily for at least 3 doses, after which they could switch to oral 600 mg twice daily.

For the primary efficacy endpoint, the percentages of subjects in the intent-to-treat population with favorable early clinical responses at the early assessment visit (48-72 hours after the start of study drug) were 77.9% in the contezolid acefosamil group and 78.5% in the linezolid group.

Outcomes were also similar in the ITT population at the post-therapy evaluation visit (7-14 days after end of therapy [EOT]), with favorable responses of 76.3% in the contezolid acefosamil group and 73.8% in the linezolid group.

Similar results between the study groups were observed in other secondary efficacy outcomes in clinically evaluable and microbiological populations at the EA, EOT, and PTE visits.

Methicillin-resistant Staphylococcus aureus (MRSA) was the most commonly identified pathogen, and efficacy outcomes were similar in subjects between the two study arms with MRSA infections.

The overall incidence of treatment-emergent adverse events (TEAEs) was similar between the study arms, including TEAEs considered to be related to study drug (contezolid acefosamil 16.3%, linezolid 14.1%).

Nausea and vomiting were the most common TEAEs, and most were mild or moderate in severity.

There were no drug-related TEAEs considered to be serious or that led to discontinuation of study drug.

Overall, safety laboratory changes were similar, though the proportions of subjects with neutrophil and platelet values that were below the lower limit of normal or substantially abnormal were lower in the contezolid acefosamil group than in the linezolid group (neutrophils: contezolid acefosamil below LLN 3.7% and SA 0%, linezolid below LLN 7.4% and SA 3.7%; platelets: contezolid acefosamil below LLN 7.6% and SA 2.5%, linezolid below LLN 12.1% and SA 5.2%).

MicuRx Pharmaceuticals is a clinical-stage biopharmaceutical company focused on the discovery, development, and commercialisation of antimicrobial therapeutics for multidrug-resistant "superbug" infections.

Since our inception in 2007, we have leveraged our management team's extensive experience in the discovery and development of novel antimicrobial agents, and our scientists in the US and China have built a pipeline that includes contezolid (MRX-I), contezolid acefosamil (MRX-4), MRX-8 (novel polymyxin MDR Gram-negative agent), and MRX-12 (new class MDR Gram-negative agent). Our mission is to combat pathogens on the WHO list of "superbugs."

Its lead compound, contezolid (MRX-I), a next-generation oxazolidinone targeting methicillin-resistant Staphylococcus aureus (MRSA), was structure-designed to reduce the hematologic toxicity and monoamine oxidase inhibition risk of this antibiotic class.

In 2015, MicuRx completed two independent Phase 2 studies in the US and China for oral contezolid, and in 2019, completed a Phase 3 study in China for the treatment of complicated skin and soft tissue infections (cSSTI). Contezolid acefosamil (MRX-4) is a prodrug of contezolid and is planned for global development in battling MDR Gram-positive infections with both oral and IV formulations.

Both contezolid and contezolid acefosamil have been granted QIDP designation and Fast Track status by the US FDA. MicuRx has R and D centers outside of San Francisco, California, and in Shanghai, China.

The company has raised a total of USD107 m through leading venture capital firms including Morningside Ventures, BVCF, GP Healthcare Capital, GP TMT Capital, 3E Bioventures Capital, and Delian Capital.