Cross-Resistance

Some emerging resistance to aztreonam, ceftazidime, ciprofloxacin, imipenem, or meropenem were observed in the TOBI Podhaler clinical trials. As other anti-pseudomonal antibiotics were concomitantly utilized in many patients in the clinical trials, the association with TOBI Podhaler is not clear.

Other

No trends were observed in the isolation of treatment-emergent bacterial respiratory pathogens (Burkholderia cepacia, Stenotrophomonas maltophilia, Staphylococcus aureus and Achromobacter xylosoxidans).

13 NONCLINICAL TOXICOLOGY
 

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
Carcinogenicity studies were not conducted with TOBI Podhaler. A two-year rat inhalation toxicology study to assess carcinogenic potential of TOBI (tobramycin inhalation solution, USP) has been completed. Rats were exposed to TOBI for up to 1.5 hours per day for 95 weeks. Serum levels of tobramycin of up to 35 µg/mL were measured in rats, in contrast to the maximum 1.99 ± 0.59 µg/mL level observed in cystic fibrosis patients in TOBI Podhaler clinical trials. There was no drug-related increase in the incidence of any variety of tumor.

Additionally, tobramycin has been eva luated for genotoxicity in a battery of in vitro and in vivo tests. The Ames bacterial reversion test, conducted with 5 tester strains, failed to show a significant increase in revertants with or without metabolic activation in all strains. Tobramycin was negative in the mouse lymphoma forward mutation assay, did not induce chromosomal aberrations in Chinese hamster ovary cells, and was negative in the mouse micronucleus test.

Subcutaneous administration of up to 100 mg/kg of tobramycin did not affect mating behavior or cause impairment of fertility in male or female rats.

14 CLINICAL STUDIES
The Phase 3 clinical development program included two placebo-controlled studies (Studies 2 and 3) and one open-label study (Study 1), which randomized and dosed 157 and 517 patients, respectively, with a clinical diagnosis of cystic fibrosis, confirmed by quantitative pilocarpine iontophoresis sweat chloride test, well-characterized disease causing mutations in each CFTR gene, or abnormal nasal transepithelial potential difference characteristic of cystic fibrosis.

In the placebo-controlled studies, all patients were aged between 6 and 21 years old and had an FEV1 at screening within the range of 25% to 80% (inclusive) of predicted normal values for their age, sex, and height based upon Knudson criteria. In addition, all patients were infected with P. aeruginosa as demonstrated by a positive sputum or throat culture (or bronchoalveolar lavage) within 6 months prior to screening, and also in a sputum culture taken at the screening visit. Among the 76 patients treated with TOBI Podhaler, 37% were males and 63% were females. Thirty-six patients were between 6 and 12 years of age, and 40 patients were between 13 and 21 years of age. Patients had a mean baseline FEV1 of 56% of predicted normal value.

In both studies, >90% of patients received concomitant therapies for cystic fibrosis related indications. The most frequently used other antibacterial drugs (any route of administration) were azithromycin, ciprofloxacin, and ceftazidime. Consistent with the population of cystic fibrosis patients, the most frequently used concomitant medications included oral pa