Safety, efficacy, and pharmacokinetics of navitoclax (ABT-263) in combination with irinotecan: results of an open-label, phase 1 study.

PURPOSE: The oral Bcl-2 inhibitor navitoclax demonstrated activity in solid and hematologic malignancies as monotherapy and in combination with other cytotoxic agents in preclinical and early clinical studies. We evaluated the safety, pharmacokinetics (PK), and antitumor activity of navitoclax plus irinotecan. METHODS: In this multicenter, open-label, phase 1 dose escalation study, adults with advanced solid tumors received navitoclax (starting dose 150 mg/day) in combination with 1 of 2 irinotecan schedules during a 21-day cycle: a once-every-3-week regimen (Q3W 180, 250, or 350 mg/m(2)) or a once-weekly regimen (QW 75 or 100 mg/m(2)). Enrollment occurred until a maximum tolerated dose (MTD) and/or recommended phase 2 dose (RPTD) was reached. RESULTS: All patients (Q3W, n = 14; QW, n = 17) were evaluable for safety, PK, and efficacy. The most common adverse event in both groups was diarrhea (Q3W 92.9 %; QW 76.5 %), which was the most frequent grade 3/grade 4 adverse event (Q3W 42.9 %; QW 29.4 %). The study was amended to exclude 4 UGT1A1*28 7/7 homozygous patients due to frequent irinotecan-related grade 3/grade 4 diarrhea and/or febrile neutropenia. No apparent PK interactions between navitoclax and irinotecan were observed. The MTD of the combination was exceeded in the Q3W group at the lowest dose administered. In the QW group, the MTD and RPTD for navitoclax were 150 mg when combined with irinotecan 75 mg/m(2). One patient in each group achieved a partial response. CONCLUSION: The RPTD of navitoclax in combination with irinotecan 75 mg/m(2) QW during a 21-day cycle was 150 mg in these heavily pretreated patients.

Safety, efficacy, and pharmacokinetics of navitoclax (ABT-263) in combination with erlotinib in patients with advanced solid tumors.

PURPOSE: Navitoclax (ABT-263), a novel, oral Bcl-2 inhibitor, enhances the antitumor effects of chemotherapy in vitro by lowering the apoptotic threshold. This phase I study (NCT01009073) evaluated the safety, pharmacokinetics, and preliminary antitumor activity of navitoclax combined with erlotinib in patients with advanced solid tumors. PATIENTS AND METHODS: An open-label dose escalation study included an arm evaluating navitoclax combined with erlotinib, which included a dose escalation cohort and a planned safety expansion cohort. Patients with documented cancers for whom erlotinib therapy was appropriate received erlotinib 150 mg orally once daily plus navitoclax 150 mg orally once daily, with navitoclax dose escalation via a continuous reassessment method model. RESULTS: Eleven patients were enrolled, including six patients with nonsmall cell lung cancer. Dose-limiting toxicities, most commonly diarrhea, were observed in 4 patients. Navitoclax dosing remained at 150 mg/day because the maximum tolerated dose was exceeded at this starting dose. The planned dose escalation did not occur; no recommended phase II dose (RPTD) was identified, and there was no safety expansion cohort. The most common treatment-related adverse events were diarrhea, nausea, vomiting, and decreased appetite. Pharmacokinetic analysis showed no apparent interactions between co-administered navitoclax and erlotinib. No objective responses were observed; the disease control rate was 27 % (95 % CI, 6-61 %). CONCLUSION: At the erlotinib and navitoclax doses administered, RPTD was not reached, but the safety profile of the combination was consistent with data from monotherapy studies. There were no apparent pharmacokinetic interactions between erlotinib and navitoclax. Three patients had stable disease.

Phase II study of single-agent navitoclax (ABT-263) and biomarker correlates in patients with relapsed small cell lung cancer.

PURPOSE: Bcl-2 is a critical regulator of apoptosis that is overexpressed in the majority of small cell lung cancers (SCLC). Nativoclax (ABT-263) is a potent and selective inhibitor of Bcl-2 and Bcl-x(L). The primary objectives of this phase IIa study included safety at the recommended phase II dose and preliminary, exploratory efficacy assessment in patients with recurrent and progressive SCLC after at least one prior therapy. EXPERIMENTAL DESIGN: Thirty-nine patients received navitoclax 325 mg daily, following an initial lead-in of 150 mg daily for 7 days. Study endpoints included safety and toxicity assessment, response rate, progression-free and overall survival (PFS and OS), as well as exploratory pharmacodynamic correlates. RESULTS: The most common toxicity associated with navitoclax was thrombocytopenia, which reached grade III-IV in 41% of patients. Partial response was observed in one (2.6%) patient and stable disease in 9 (23%) patients. Median PFS was 1.5 months and median OS was 3.2 months. A strong association between plasma pro-gastrin-releasing peptide (pro-GRP) level and tumor Bcl-2 copy number (R = 0.93) was confirmed. Exploratory analyses revealed baseline levels of cytokeratin 19 fragment antigen 21-1, neuron-specific enolase, pro-GRP, and circulating tumor cell number as correlates of clinical benefit. CONCLUSION: Bcl-2 targeting by navitoclax shows limited single-agent activity against advanced and recurrent SCLC. Correlative analyses suggest several putative biomarkers of clinical benefit. Preclinical models support that navitoclax may enhance sensitivity of SCLC and other solid tumors to standard cytotoxics. Future studies will focus on combination therapies.

Substantial susceptibility of chronic lymphocytic leukemia to BCL2 inhibition: results of a phase I study of navitoclax in patients with relapsed or refractory disease.

PURPOSE: BCL2 overexpression is a hallmark of chronic lymphocytic leukemia (CLL). The novel BH3 mimetic navitoclax (ABT-263) specifically inhibits BCL2 and related proteins BCL-x(l) and BCL-w, potently inducing apoptosis of CLL cells in vitro. A phase I trial in patients with CLL was conducted to evaluate the safety, pharmacokinetics, and biologic activity of oral navitoclax. PATIENTS AND METHODS: Twenty-nine patients with relapsed or refractory CLL received daily navitoclax for 14 days (10, 110, 200, or 250 mg/d; n = 15) or 21 days (125, 200, 250, or 300 mg/d; n = 14) of each 21-day cycle. Dose escalation decisions were informed by continual reassessment methodology. RESULTS: Lymphocytosis was reduced by more than 50% in 19 of 21 patients with baseline lymphocytosis. Among 26 patients treated with navitoclax ≥ 110 mg/d, nine (35%) achieved a partial response and seven maintained stable disease for more than 6 months. Median treatment duration was 7 months (range, 1 to ≥ 29 months). Median progression-free survival was 25 months. Activity was observed in patients with fludarabine-refractory disease, bulky adenopathy, and del(17p) CLL. Thrombocytopenia due to BCL-x(l) inhibition was the major dose-limiting toxicity and was dose-related. Low MCL1 expression and high BIM:MCL1 or BIM:BCL2 ratios in leukemic cells correlated with response. We determined that the navitoclax dose of 250 mg/d in a continuous dosing schedule was optimal for phase II studies. CONCLUSION: BCL2 is a valid therapeutic target in CLL, and its inhibition by navitoclax warrants further evaluation as monotherapy and in combination in this disease.

Role for 5-day, once-daily extended-release clarithromycin in acute bacterial exacerbation of chronic bronchitis.

BACKGROUND: Clarithromycin is commonly dosed for 7 or more days in patients with acute bacterial exacerbation of chronic bronchitis (ABECB). Studies with other antibiotics have shown equivalent efficacy, reduced/similar frequency of adverse events, improved adherence and patient satisfaction, and lower treatment costs with a shorter treatment course. PATIENTS AND METHODS: The study population was derived from two multicenter, randomized, double-blind (North America)/single-blind (France) comparative trials in which outpatients at least 35 years old with a presumptive diagnosis of obstructive ABECB were randomized to receive clarithromycin extended-release (ER) 1000 mg once daily for 5 days or a comparator agent--clarithromycin immediate-release (IR) 500 mg twice daily for 7 days (in North America) or telithromycin 800 mg once daily for 5 days (in France). RESULTS: A total of 818 patients were randomized (411 to clarithromycin ER and 407 to a comparator agent). The clinical cure rate in clinically evaluable patients at the follow-up visit was 90% each for the clarithromycin ER group (318/353) and the comparator group (318/355). The patient bacteriological cure rate and the overall target pathogen eradication rate in clinically and bacteriologically evaluable patients were each 92% for the clarithromycin ER group (155/168 and 189/205, respectively) and 93% for the comparator group (147/158 and 183/197, respectively) at the follow-up visit. The study drugs were generally well tolerated, with < 2% of patients discontinuing their treatment prematurely due to a drug-related adverse event. The incidence of drug-related adverse events was 18% (73/411) in the clarithromycin ER group and 24% (97/407) in the comparator group. Clarithromycin ER-treated patients reported statistically significantly fewer episodes of abdominal pain than did patients treated with a comparator agent (0.2% vs. 1.7%, respectively; p = 0.037). This combined analysis is limited by differing blinding methods, comparator agents, and their duration of administration. Furthermore, many patients were excluded from the clinically and bacteriologically evaluable group due to lack of a pretreatment target pathogen. CONCLUSION: A once daily, 5-day clarithromycin ER regimen appears to be a suitable choice for treating patients with ABECB.

Efficacy, tolerability, and parent reported outcomes for cefdinir vs. high-dose amoxicillin/clavulanate oral suspension for acute otitis media in young children.

OBJECTIVES: To compare efficacy, tolerability, and parental satisfaction of cefdinir and high-dose amoxicillin/clavulanate oral suspensions given to young children with non-refractory acute otitis media (AOM) based on clinical endpoints and outcomes measures. RESEARCH DESIGN AND METHODS: This was an investigator-blinded, multicenter study in which 318 children 6 months through 6 years of age with a clinical diagnosis of AOM were randomized to receive 10 days of either cefdinir (14 mg/kg divided BID) or high-dose amoxicillin/clavulanate (90/6.4 mg/kg divided BID). MAIN OUTCOME MEASURES: Investigators evaluated clinical response at an end-of-therapy (EOT) office visit conducted on day 12-15. Outcomes of satisfaction, tolerability, and adherence were also assessed at that visit using an Otitis Parent Questionnaire. RESULTS: The treatment groups were similar at baseline with respect to patient demographics. At the EOT visit, for cefdinir and amoxicillin/clavulanate, respectively, intent-to-treat (ITT) clinical cure rates were 82% (129/158) and 85% (134/158) (p = 0.547; 95% confidence interval [CI] -11.7 to 5.4) and per-protocol cure rates were 82% (123/150) and 90% (129/143) (p = 0.045; 95% CI -16.4 to 0.0). This difference was driven primarily by reduced cefdinir response in patients with recurrent AOM (p = 0.010) and those younger than 24 months (p = 0.039). Comparing cefdinir with amoxicillin/clavulanate, parents more often reported significantly better ease of use (89% vs. 57%; p < 0.0001), better taste (85% vs. 39%; p < 0.0001), and better adherence (at least 95% of doses) (82% vs. 61%; p < 0.0001). Diarrhea/loose stools were more common in the amoxicillin/clavulanate group than in the cefdinir group (28% vs. 18%, respectively; p = 0.0341). One patient in the cefdinir group and eight patients in the amoxicillin/clavulanate group withdrew from the study prematurely due to at least one adverse event (p = 0.0364). Study limitations included assessment of clinical recurrence by telephone call rather than office visit, exclusion of children with refractory AOM, and no assessment of middle ear microbiology. CONCLUSIONS: Among young children with non-refractory AOM, cefdinir was as efficacious as high-dose amoxicillin/clavulanate in the ITT group, but somewhat less effective in per-protocol analysis. From the parental perspective, cefdinir was easier to administer, had a better taste, caused less diarrhea, and resulted in higher treatment adherence than high-dose amoxicillin clavulanate.

Cefdinir vs. cephalexin for mild to moderate uncomplicated skin and skin structure infections in adolescents and adults.

OBJECTIVES: To compare the efficacy and safety of cefdinir to that of cephalexin in adolescents and adults with mild to moderate uncomplicated skin and skin structure infections (USSSI). RESEARCH DESIGN AND METHODS: This was an investigator-blinded, multicenter study in which patients at least 13 years of age with USSSI were randomized to receive 10 days of cefdinir 300 mg twice daily (BID) or cephalexin 250 mg four times daily (QID). Patients were evaluated at baseline, by telephone on Days 3-5, and during office visits on Days 12-14 (end-of-therapy [EOT] visit) and Days 17-24 (test-of-cure [TOC] visit). MAIN OUTCOME MEASURES: Clinical response was evaluated at the TOC visit. Patient reported outcomes, including a usefulness questionnaire, were also assessed. RESULTS: Three hundred and ninety-one patients were treated. The treatment groups were well matched with regard to demographic characteristics and types of infection. Abscess(es) (26%), wound infection (24%), and cellulitis (21%) were the most common infections. At the TOC visit, the clinical cure rate for both treatment groups was 89% (151/170 for cefdinir and 154/174 for cephalexin) in clinically evaluable patients (95% CI for difference in cure rates [-6.7 to 7.3]). In the intent-to-treat analysis, cure rates were 83% for cefdinir vs. 82% for cephalexin. Clinical cure rates for infections caused by methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus were 93% (37/40) and 92% (35/38) for cefdinir vs. 91% (29/32) and 90% (37/41) for cephalexin (p > 0.999 comparing treatment groups for MSSA; p > 0.999 for MRSA). The usefulness questionnaire demonstrated that cefdinir was more highly rated in the mean composite score (87.4 vs. 83.6, p = 0.04), with the difference primarily due to the respondents' preference for the convenience of taking the study medication (mean score 93.5 vs. 74.1 for cephalexin, p < 0.001). The study had the following limitations: the requirement for culture at baseline likely skewed the enrollment of patients towards those with abscesses; the results of culture in patients with USSSIs are often nonspecific; in some patients entering the study with a diagnosis of cellulitis, the cellulitis was associated with an abscess; and, incision and drainage (I&D), spontaneous drainage, and needle aspiration are likely to have contributed to clinical response for purulent infections, and in particular MRSA-associated infections. Both study drugs were well tolerated. The most common treatment-related adverse events were diarrhea (10% cefdinir, 4% cephalexin, p = 0.017), nausea (3% and 6%, respectively, p = 0.203), and vaginal mycosis (3% and 6% of females, respectively, p = 0.500). CONCLUSIONS: This study demonstrated that empiric coverage of USSSIs with cephalosporin therapy remains an appropriate clinical strategy. MRSA infections responded well in both arms of the study, suggesting that the choice of a cephalosporin did not adversely affect patient outcome. However, cephalosporins do not have accepted, clinically relevant in vitro activity against MRSA. Hence, the clinical response rates seen in this study against MRSA infections must be interpreted with caution. Cefdinir was more highly rated than cephalexin in a composite usefulness assessment.

Once daily clarithromycin extended-release vs twice-daily amoxicillin/clavulanate in patients with acute bacterial sinusitis: a randomized, investigator-blinded study.

OBJECTIVE: To compare the efficacy and tolerability of clarithromycin extended-release (ER) to amoxicillin/ clavulanate in patients diagnosed with acute bacterial sinusitis. RESEARCH DESIGN AND METHODS: In a controlled, multicenter, investigator-blinded study, 437 ambulatory patients at least 12 years old with signs/symptoms and radiographic findings of acute sinusitis were randomized to receive clarithromycin ER 1000 mg once daily or amoxicillin/ clavulanate 875 mg/l25 mg twice daily for 14 days. MAIN OUTCOME MEASURES: Clinical and bacteriological response rates were determined at a test-of-cure visit, which was conducted up to 10 days following the completion of treatment. Radiological response was assessed at a follow-up visit. RESULTS: The clinical cure rate in clinically evaluable patients was 98% (184/188) in the clarithromycin ER group and 97% (179/185) in the amoxicillin/clavulanate group (95% CI for the difference in rates [-2.4%, 4.7%]). Clinical cure was sustained at the follow-up visit (96% for each treatment group). The pathogen eradication rates were 94% (61/65) in the clarithromycin ER group and 98% (61/62) in the amoxicillin/clavulanate group (95% CI for difference in rates [-12.0%, 2.9%]). The radiological success rate was 94% (172/183) in both the clarithromycin ER and amoxicillin/clavulanate groups (95% CI for difference in rates [-4.9%, 4.9%]). Symptomatic improvement or relief was observed as early as 2 days-5 days after the initiation of study drug, with a statistically significantly higher resolution rate of sinus pressure (p = 0.027) and improvement/resolution rate of nasal congestion (p = 0.035) during treatment with clarithromycin ER. The resolution/improvement rate at the test-of-cure visit for each treatment group was > or = 94% for the primary acute sinusitis signs/symptoms, with a statistically significantly higher resolution/improvement rate of purulent nasal discharge with clarithromycin ER (p = 0.010). Both study drugs had a positive and rapid impact on quality of life. Patients reported a high level of satisfaction and probability of using either study antibiotic again, and health care resource use was low, with slightly fewer sinusitis-related physician and outpatient visits required by patients in the clarithromycin ER group (p = 0.055). The treatment groups were comparable with respect to incidence of drug-related adverse events. CONCLUSION: In this multinational population of patients with acute bacterial sinusitis, clarithromycin ER was comparable, and for selected measures superior, to amoxicillin/clavulanate based on clinical, bacteriological, and radiological responses as well as quality of life measures, satisfaction with antibiotic therapy, and health care resource utilization.

Comparison of five-day cefdinir treatment with ten-day low dose amoxicillin/clavulanate treatment for acute otitis media.

BACKGROUND: Short course beta-lactam antibiotic therapy for acute otitis media (AOM) should improve patient adherence, but it has not been evaluated since the heptavalent pneumococcal conjugate vaccine became routinely used in the United States. METHODS: In a prospective, investigator-blinded, multicenter study, 425 patients, age 6 months-6 years, with a clinical diagnosis of nonrefractory AOM were randomized to receive either 5 days of cefdinir therapy (14 mg/kg divided twice daily) or 10 days of amoxicillin/clavulanate therapy (45/6.4 mg/kg divided twice daily). Clinical response was assessed at end of therapy (2-4 days postantibiotic, respectively) and week 4 (study days 25-28). RESULTS: With no difference in demographics between treatment groups, overall the mean age (+/-SD) was 2.8 +/- 1.8 years, 65% had received conjugated pneumococcal vaccination and 48% had bilateral AOM. The satisfactory clinical response rate at end of therapy was comparable for cefdinir versus amoxicillin/clavulanate (88%, 170 of 194 versus 85%, 164 of 192; 95% CI -4.9, 9.3). Although this must be interpreted with caution, cefdinir showed an apparent trend for higher efficacy than amoxicillin/clavulanate (92%, 72 of 78 versus 77%, 55 of 71; P = 0.019) in a subsample of patients 6-24 months old who had received conjugated pneumococcal vaccination. The incidence of drug-related adverse events was less for cefdinir than for amoxicillin/clavulanate (24%, 50 of 211 versus 38%, 82 of 214; P = 0.0018) CONCLUSION: For children with nonrefractory AOM, based only on clinical endpoints, 5 days of therapy with cefdinir 14 mg/kg divided twice daily was comparable overall with 10 days of therapy with low dose amoxicillin/clavulanate 45/6.4 mg/kg divided twice daily.

Cefdinir versus levofloxacin in patients with acute rhinosinusitis of presumed bacterial etiology: a multicenter, randomized, double-blind study.

BACKGROUND: Treatment guidelines for acute bacterial rhinosinusitis (ABRS) recommend 10 to 14 days of therapy with high-dose amoxicillin, amoxicillin/clavulanate, cefdinir, cefpodoxime, cefuroxime, a macrolide, or a newer fluoroquinolone, among other agents. OBJECTIVE: This study compared the clinical efficacy and tolerability of cefdinir and levofloxacin in patients with a diagnosis of acute rhinosinusitis of presumed bacterial origin. METHODS: In this multicenter, double-blind, noninferiority study, ambulatory adult patients who had signs and symptoms for >7 to 21 days before the screening visit and radiographic findings consistent with acute rhinosinusitis were randomized to receive cefdinir 600 mg or levofloxacin 500 mg, each once daily for 10 days. Clinical and radiologic response rates were determined at the test-of-cure (TOC) visit, which took place 9 to 14 days after the completion of treatment. RESULTS: Two hundred seventy-one patients (138 cefdinir, 133 levofloxacin) were enrolled and randomized to treatment at 27 study centers in the United States and Poland between November 2003 and March 2004. Of these, 241 (123 cefdinir, 118 levofloxacin) were clinically evaluable. The cefdinir group consisted of 75 women and 48 men, of whom 117 were white and 6 black; their mean (SD) age was 42.5 (14.3) years. The levofloxacin group consisted of 71 women and 47 men, of whom 111 were white and 7 black; their mean age was 40.4 (13.6) years. The 2 groups were similar in terms of presenting signs and symptoms and baseline radiographic findings. The most common presenting symptoms were sinus pain, sinus pressure, and purulent nasal discharge, each of which was reported by > or =89% of patients. Clinical cure rates at the TOC visit in the cefdinir and levofloxacin groups were 83% (102/123) and 86% (101/118), respectively (95% Cl for the difference in cure rates, -12.3 to 7.0). Cefdinir and levofloxacin were comparable in the treatment of infections classified as moderate to severe. The incidence of drug-related adverse events was generally comparable in the 2 treatment groups, although there were significant differences between cefdinir and levofloxacin in the incidence of vaginal moniliasis in women (11% vs 0%, respectively; P = 0.003), drug-related diarrhea (8% vs 1%; P = 0.005), and insomnia (0% vs 4%; P = 0.027). Only 2% of patients discontinued therapy prematurely as a result of a drug-related adverse event. CONCLUSION: In this population of patients with ABRS, the extended-spectrum cephalosporin cefdinir was as efficacious as the fluoroquinolone levofloxacin, suggesting that cefdinir may be a suitable alternative to the currently recommended fluoroquinolones.

A controlled, double-blind, multicenter study comparing clarithromycin extended-release tablets and levofloxacin tablets in the treatment of community-acquired pneumonia.

BACKGROUND: Macrolides and fluoroquinolones are frequently used for the empiric treatment of community-acquired pneumonia (CAP). OBJECTIVE: The aim of the study was to compare the safety profile and efficacy of clarithromycin extended-release (ER) tablets with those of levofloxacin tablets for the treatment of CAP in ambulatory adult patients. METHODS: In a Phase III, double-blind, randomized, parallel-group, multicenter study, ambulatory adult patients (> or = 18 years) with signs and symptoms of CAP received a 7-day course of treatment with either clarithromycin ER (two 500-mg tablets once daily) or levofloxacin (two 250-mg tablets once daily). A diagnosis of CAP was confirmed by radiography of the chest and physical examination, and sputum samples were analyzed to identify etiologic pathogen(s). Tolerability was assessed through subjective reports of adverse events and through changes in physical findings, concomitant medications, and laboratory values. RESULTS: There were no statistically significant differences between treatment groups in terms of sex, age, race, or body weight. The mean age was 50 years (range, 18-91 years). Of 299 patients randomized and treated, 252 were clinically evaluable (128 clarithromycin ER, 124 levofloxacin). The 95% CI for the difference between cure rates demonstrated equivalence of the 2 treatments. Among clinically evaluable patients at the test-of-cure visit, clinical cure rates were 88% (113/128) and 86% (107/124), and radiographic success rates were 95% (117/123) and 88% (104/118) for clarithromycin ER and levofloxacin, respectively. Both treatment regimens were effective in resolving and improving clinical signs and symptoms of CAP. Among clinically and bacteriologically evaluable pa- tients, bacteriologic cure rates were 86% (80/93) and 88% (85/97) for clarithromycin ER and levofloxacin, respectively. No statistically significant differences were observed between the 2 treatment groups in the overall incidence of adverse events. CONCLUSIONS: Clarithromycin ER demonstrated equivalent efficacy and tolerability to the fluoroquinolone levofloxacin in a group of ambulatory adult patients with CAP. Clarithromycin ER also appeared to be safe in the population studied.

A prospective, double-blind, multicenter study comparing clarithromycin extended-release with trovafloxacin in patients with community-acquired pneumonia.

BACKGROUND: Treatment guidelines for community-acquired pneumonia (CAP) generally include use of a macrolide, a fluoroquinolone, or doxycycline, although there is some debate concerning the use of a fluoroquinolone. OBJECTIVE: The efficacy and tolerability of a new once-daily, extended-release (ER) formulation of clarithromycin were compared with those of a fluoroquinolone, trovafloxacin, in the treatment of patients with CAP. METHODS: This was a prospective, multicenter, double-blind, double-dummy, parallel-group trial in which outpatients were randomized to receive 7 days of once-daily treatment with either clarithromycin ER (two 500-mg tablets) or trovafloxacin (200 mg). Eligible patients were > or = 18 years old with signs and symptoms of pneumonia, radiologic evidence of an acute infiltrate, and mild to moderate infection, as classified by the investigator. RESULTS: One hundred seventy-six patients were randomized to study treatment. They were primarily white (88%) and equally distributed between the sexes (52% female). Their mean (+/-SD) age was 47.5 +/- 16.2 years. Results were similar between treatment groups in rates of clinical cure, microbiologic cure, bacteriologic eradication, and radiologic success at the test-of-cure visit (14-21 days posttreatment) for both the per-protocol and intent-to-treat analyses. Among clinically evaluable patients, clinical cure rates for clarithromycin ER and trovafloxacin were 87% (74/85) and 95% (63/66), respectively, and radiologic success rates were 95% (80/84) and 95% (63/66), respectively. There were no statistically significant differences between groups. In clinically and microbiologically evaluable patients, overall bacteriologic eradication rates were 89% (85/95) for clarithromycin ER and 96% (64/67) for trovafloxacin, with no significant differences between groups. Both antibiotics demonstrated high eradication rates against target microorganisms. There were no clinically meaningful differences in the incidence of specific drug-related adverse events. The majority of drug-related adverse events (>90%) were considered mild or moderate and resolved without the need for additional treatment. CONCLUSIONS: Although the study was prematurely terminated, resulting in inadequate power to demonstrate equivalence, once-daily clarithromycin ER was effective and well tolerated in the treatment of ambulatory adult (age > or = 18 years) outpatients with CAP.