Investors in Cempra Inc (NASDAQ:CEMP) should be smiling from ear to ear this morning following the news that the drug maker achieved positive topline results from a phase 3 study of oral fusidic acid in 716 patients with acute bacterial skin and skin structure infections (ABSSSI). Fusidic acid was well tolerated in the study and achieved the primary endpoint, demonstrating non-inferiority (NI) (10% NI margin) of oral fusidic acid compared to oral linezolid for early clinical response (ECR) in the intent to treat (ITT) patient population.

Cempra shares reacted to the news, rising nearly 40% to $4.39 in pre-market trading Friday

Study Design and Demographics

The double-blind study was conducted at 62 sites in the United States. Patients randomized to treatment with oral fusidic acid received a loading dose of 1500 mg every 12 hours for two doses, followed by 600 mg every 12 hours thereafter, until the end of a 10 day course of therapy. Patients randomized to treatment with the active comparator, oral linezolid, received 600 mg every 12 hours for 10 days. Randomization was 1:1 and was stratified by type of infection (cellulitis, wound infection, major cutaneous abscess), by age and by prior use of an antibiotic within 36 hours prior to randomization.

Overall, 67.5 percent of study subjects had an infection associated with intravenous drug abuse. Less than five percent of study subjects received an antibiotic prior to randomization.

Balanced Baseline Demographic Characteristics

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Consistent Efficacy at ECR, End-of-Treatment (EOT) and Post-therapy Evaluation (PTE) 

The primary endpoint, ECR in the ITT population, was defined as the proportion of patients alive and achieving a ≥ 20 percent reduction from baseline in lesion size at 48-72 hours after the start of study drug, without receiving rescue antibiotics. In the study, 87.2 percent of ITT patients receiving fusidic acid demonstrated ECR, compared to 86.6 percent of ITT patients receiving linezolid (treatment difference 0.6%, 95% confidence interval (CI) -4.6, +5.9), demonstrating non-inferiority to linezolid.

Fusidic acid also showed comparable efficacy to linezolid in investigator-assessed clinical response in the ITT and clinically evaluable (CE) populations at EOT and PTE (7-14 days post-EOT) visits.

Clinical Response by Population

Strong Activity Against Key Pathogens, Including MRSA

Microbiological response rates by pathogen were high in both treatment groups in both the microbiological ITT (mITT) and microbiologically-evaluable (ME) patient populations (patients with isolation of a baseline pathogen, who were also clinically evaluable). The most common pathogens identified were Staphylococcus aureus, Streptococcus anginosus group species, Streptococcus pyogenes and Clostridium species. Notably, the microbiological success rate among fusidic acid recipients in each ME population with methicillin-resistant S. aureus (MRSA) infection was 100 percent (99/99) at both the EOT and PTE visits.

Fusidic Acid Well Tolerated

Fusidic acid was well tolerated in the study. The rates of treatment-emergent adverse events (TEAEs) were comparable between treatment groups (37.9 percent fusidic acid, 36.1 percent linezolid). The most common TEAEs in both treatment groups were gastrointestinal events (22.8 percent fusidic acid, 18.2 percent linezolid). Serious adverse events (SAEs) occurred in six fusidic acid recipients and eight linezolid recipients, and were considered study-drug related in one fusidic acid recipient (vomiting) and in two linezolid recipients (one drug induced liver injury, one vomiting). Adverse events led to study drug discontinuation in 2.2 percent of fusidic acid recipients, and 2.0 percent of linezolid recipients. There was one death in the study, an event due to illicit drug overdose and aspiration which occurred in a patient receiving linezolid. Rates of treatment-emergent ALT elevation to > 3x ULN occurred in 1.0 percent of fusidic acid recipients and 0.7 percent of linezolid patients.

“Considering complicated skin infections are one of the most rapidly growing reasons for hospitalizations and emergency department visits each year, the results with fusidic acid in this study are promising, especially for an outpatient population where there is a need for new oral drugs that are effective against MRSA,” said William O’Riordan, M.D., chief medical officer of eStudySite, leaders in evaluating new therapeutic approaches for complicated skin infections.

Cempra plans to submit the full data from this study for presentation at an upcoming scientific forum.

“We are excited that the results of this phase 3 study with fusidic acid confirm the results of our phase 2 study and are consistent with the more than 40 years of experience that the product has accumulated outside the United States,” said David Oldach, M.D., chief medical officer of Cempra.

“We look forward to meeting with the FDA to discuss the next steps required to bring fusidic acid to patients in the United States,” Oldach added.

On the ratings front, Cempra has been the subject of a number of recent research reports. In a report issued on January 12, J.P. Morgan analyst Jessica Fye maintained a Hold rating on CEMP, while on December 30, Morgan Stanley’s Andrew Berens upgraded the stock to Hold.

According to TipRanks.com, which ranks over 7,500 financial analysts and bloggers to gauge the performance of their past recommendations, Jessica Fye and Andrew Berens have a yearly average loss of -14.4% and a return of 12.6% respectively. Fye has a success rate of 33% and is ranked #4261 out of 4499 analysts, while Berens has a success rate of 70% and is ranked #482.

Sentiment on the street is mostly neutral on CEMP stock. Out of 11 analysts who cover the stock, 8 suggest a Hold ratin , 2 suggest a Sell and one recommends to Buy the stock. The 12-month average price target assigned to the stock is $2.50, which represents a potential downside of 21% from where the stock is currently trading.

Cempra, Inc. engages as a clinical-stage pharmaceutical company, which focuses on the development of antibacterials to meet critical medical needs. Its products include; Solithromycin and Taksta.