Standards for Treatment and Control Regimens in Therapeutic Trials for Gonorrhea: Lessons From a “Failed” Trial

Treatment efficacy for pharyngeal Neisseria gonorrhoeae: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Rising gonorrhoea rates require highly effective treatments to reduce transmission and prevent development of antimicrobial resistance. Currently the most effective treatments for pharyngeal gonorrhoea remain unclear. This review aimed to estimate treatment efficacy for pharyngeal gonorrhoea.

METHODS

Online bibliographic databases were searched for the period 1 January 2000 to 17 September 2019 for treatments of gonorrhoea. All randomized controlled trials (RCTs) with data on pharyngeal gonorrhoea among participants aged 15 years or above, published in English, were included. Meta-analyses (random effects) were used to estimate the treatment efficacy, defined as microbiological cure, among currently recommended monotherapies and dual therapies, previously recommended but no longer used regimens and emerging drugs under evaluation. Side effects were also summarized. The study protocol was registered on PROSPERO (CRD42020149278).

RESULTS

There were nine studies that included 452 participants studying 19 treatment regimens. The overall treatment efficacy for pharyngeal gonorrhoea was 98.1% (95% CI: 93.8%-100%; I2 = 57.3%; P < 0.01). Efficacy was similar for single (97.1%; 95% CI: 90.8%-100.0%; I2 = 15.6%; P = 0.29) and dual therapies (98.0%; 95% CI: 91.4%-100%; I2 = 79.1%; P < 0.01). Regimens containing azithromycin 2 g or ceftriaxone were similarly efficacious. The summary efficacy estimate for emerging drugs was 88.8% (95% CI: 76.9%-97.5%; I2 = 11.2%; P = 0.34). Small sample sizes in each trial was a major limitation.

CONCLUSIONS

Regimens containing ceftriaxone or azithromycin 2 g, alone or as part of dual therapies are the most efficacious for pharyngeal gonorrhoea. Further pharyngeal-specific RCTs with adequate sample sizes are needed.

Gentamicin Alone Is Inadequate to Eradicate Neisseria Gonorrhoeae From the Pharynx

BACKGROUND

Centers for Disease Control and Prevention (CDC) guidelines recommend 240 mg gentamicin plus 2 g azithromycin for the treatment of gonorrhea in cephalosporin-allergic patients. The efficacy of gentamicin alone in the treatment of pharyngeal gonorrhea is uncertain.

METHODS

Between September 2018 and March 2019, we enrolled men who have sex with men with nucleic acid amplification test-diagnosed pharyngeal gonorrhea in a single-arm, unblinded clinical trial. Men received a single 360-mg intramuscular dose of gentamicin and underwent test of cure by culture 4-7 days later. The study measured creatinine at enrollment and test of cure, serum gentamicin concentration postdose to establish peak concentration (Cmax), and standard antimicrobial minimum inhibitory concentrations (MICs) by agar dilution. The trial was designed to establish a point estimate for gentamicin's efficacy for pharyngeal gonorrhea. We planned to enroll 50 evaluable participants; assuming gentamicin was 80% efficacious, the trial would establish a 95% confidence interval (CI) of 66%-90%. We planned interim analyses at n = 10 and n = 25.

RESULTS

The study was stopped early due to poor efficacy. Of 13 enrolled men, 10 were evaluable, and only 2 (20% [95% CI, 2.5%-55.6%]) were cured. Efficacy was not associated with gentamicin Cmax or MIC. No participants experienced renal insufficiency. The mean creatinine percentage change was +5.2% (range, -6.7% to 21.3%). Six (46%) participants experienced headache, all deemed unrelated to treatment.

CONCLUSIONS

Gentamicin alone failed to eradicate Neisseria gonorrhoeae from the pharynx. Clinicians should use caution when treating gonorrhea with the CDC's current alternative regimen (gentamicin 240 mg plus azithromycin 2 g) given increases in azithromycin resistance and gentamicin's poor efficacy at the pharynx.

CLINICAL TRIALS REGISTRATION

NCT03632109.

Pharmacokinetic/pharmacodynamic considerations for new and current therapeutic drugs for uncomplicated gonorrhoea-challenges and opportunities

BACKGROUND

Increasing multidrug resistance rates in Neisseria gonorrhoeae have raised concerns and an urgent call for new antibiotics for treatment of gonorrhoea. Several decades of subdued drug development in this field and the recent failures of two new antibiotics to show non-inferiority compared with the current first-line antibiotics ceftriaxone plus azithromycin highlight the need for improved preclinical tools to predict clinical outcome of new drugs in the development process.

OBJECTIVES

To summarize current pharmacokinetic/pharmacodynamic (PK/PD) knowledge and dose-finding strategies for antibiotics against gonorrhoea.

SOURCES

Literature review of published papers and discussions by global experts at a special workshop on this topic.

CONTENT

We review current knowledge of gonococcal specific PK/PD principles and provide an update on new in vitro and in vivo models to correlate drug exposure with clinical outcome, and identify challenges and gaps in gonococcal therapeutic research.

IMPLICATIONS

Identifying the ideal antimicrobial agent and dose for treating uncomplicated urogenital and pharyngeal gonococcal disease requires appropriate validated non-clinical PK/PD models. Recent advances in adapting in vitro and in vivo models for use in gonorrhoea are an important step for enabling the development of new drugs with reduced risk of failure in Phase 3 clinical development and diminish the risk of emergence of resistance.