A dose-finding study of temsirolimus and liposomal doxorubicin for patients with recurrent and refractory bone and soft tissue sarcoma.

There are few effective therapies for high-risk sarcomas. Initial chemosensitivity is often followed by relapse. In vitro, mammalian target of rapamycin (mTOR) inhibition potentiates the efficacy of chemotherapy on resistant sarcoma cells. Although sarcoma trials using mTOR inhibitors have been disappointing, these drugs were used as maintenance. We conducted a Phase I/II clinical trial to test the ability of temsirolimus to potentiate the cytotoxic effect of liposomal doxorubicin and present here the dose-finding portion of this study. Adult and pediatric patients with recurrent or refractory sarcomas were treated with increasing doses of liposomal doxorubicin and temsirolimus using a continual reassessment method for escalation, targeting a dose-limiting toxicity rate of 20%. Blood samples were drawn before and after the first dose of temsirolimus in Cycles 1 and 2 for pharmacokinetic analysis. The maximally tolerated dose combination was liposomal doxorubicin 30 mg/m(2) monthly with temsirolimus 20 mg/m(2) weekly. Hematologic toxicity was common but manageable. Dose-limiting toxicities were primarily renal. Concurrent administration of liposomal doxorubicin resulted in increased exposure to sirolimus, the active metabolite of temsirolimus. Thus, the combination of liposomal doxorubicin and temsirolimus is safe for heavily pretreated sarcoma patients. Co-administration with liposomal doxorubicin did not alter temsirolimus pharmacokinetics, but increased exposure to its active metabolite.

Metabolic engineering of bacteria for environmental applications: construction of Pseudomonas strains for biodegradation of 2-chlorotoluene.

In this article, we illustrate the challenges and bottlenecks in the metabolic engineering of bacteria destined for environmental bioremediation, by reporting current efforts to construct Pseudomonas strains genetically designed for degradation of the recalcitrant compound 2-chlorotoluene. The assembled pathway includes one catabolic segment encoding the toluene dioxygenase of the TOD system of Pseudomonas putida F1 (todC1C2BA), which affords the bioconversion of 2-chlorotoluene into 2-chlorobenzaldehyde by virtue of its residual methyl-monooxygenase activity on o-substituted substrates. A second catabolic segment encoded the entire upper TOL pathway from pWW0 plasmid of P. putida mt-2. The enzymes, benzyl alcohol dehydrogenase (encoded by xylB) and benzaldehyde dehydrogenase (xylC) of this segment accept o-chloro-substituted substrates all the way down to 2-chlorobenzoate. These TOL and TOD segments were assembled in separate mini-Tn5 transposon vectors, such that expression of the encoded genes was dependent on the toluene-responsive Pu promoter of the TOL plasmid and the cognate XylR regulator. Such gene cassettes (mini-Tn5 [UPP2] and mini-Tn5 [TOD2]) were inserted in the chromosome of the 2-chlorobenzoate degraders Pseudomonas aeruginosa PA142 and P. aeruginosa JB2. GC-MS analysis of the metabolic intermediates present in the culture media of the resulting strains verified that these possessed, not only the genetic information, but also the functional ability to mineralise 2-chlorotoluene. However, although these strains did convert the substrate into 2-chlorobenzoate, they failed to grow on 2-chlorotoluene as the only carbon source. These results pinpoint the rate of the metabolic fluxes, the non-productive spill of side-metabolites and the physiological control of degradative pathways as the real bottlenecks for degradation of certain pollutants, rather than the theoretical enzymatic and genetic fitness of the recombinant bacteria to the process. Choices to address this general problem are discussed.