taxane and lonafarnib

The authors evaluated the safety, tolerability, and efficacy of treatment using lonafarnib, a novel farnesyltransferase inhibitor (FTI), in combination with paclitaxel in patients with metastatic (Stage IIIB/V), taxane-refractory/resistant nonsmall cell lung carcinoma (NSCLC).. Patients with NSCLC who experienced disease progression while receiving previous taxane therapy or who had disease recurrence within 3 months after taxane therapy cessation were treated with continuous lonafarnib 100 mg orally twice per day beginning on Day 1 and paclitaxel 175 mg/m(2) intravenously over 3 hours on Day 8 of each 21-day cycle.. A total of 33 patients were enrolled, 29 of whom were evaluable for response. Partial responses (PR) and stable disease (SD) were observed in 3 (10%) and 11 patients (38%), respectively. Thus, 48% (14 of 29) experienced clinical benefit (PR or SD). The updated and final median overall survival time was 39 weeks and the median disease progression-free survival time was 16 weeks. The combination of lonafarnib and paclitaxel was well tolerated with minimal toxicity. Grade 3 toxicities included fatigue (9%), diarrhea (6%), and dyspnea (6%). Grade 3 neutropenia occurred in only 1 patient (3%). Grade 4 adverse events included respiratory insufficiency in 2 patients (6%) and acute respiratory failure in 1 patient (3%).. Lonafarnib plus paclitaxel demonstrated clinical activity in patients with taxane-refractory/resistant metastatic NSCLC. In addition, the combination of lonafarnib and paclitaxel was well tolerated with minimal toxicity. Evaluation of this combination therapy in additional clinical trials is warranted.

Topics: Adult; Aged; Alkyl and Aryl Transferases; Antineoplastic Agents, Phytogenic; Bridged-Ring Compounds; Carcinoma, Non-Small-Cell Lung; Drug Therapy, Combination; Enzyme Inhibitors; Farnesyltranstransferase; Female; Humans; Lung Neoplasms; Male; Maximum Tolerated Dose; Middle Aged; Neoplasm Staging; Paclitaxel; Piperidines; Pyridines; Remission Induction; Survival Rate; Taxoids; Treatment Outcome

Lonafarnib (SCH66336) is a farnesyl transferase inhibitor (FTI) that inhibits the post-translational lipid modification of H-Ras and other farnesylated proteins. K- and N-Ras are also substrates of farnesyl transferase; however, upon treatment with FTIs, they are alternatively prenylated by geranylgeranyl transferase-1. Despite the failure to abrogate prenylation of K- and N-Ras, growth of many tumors in preclinical models is inhibited by FTIs. This suggests that the anti-proliferative action of FTIs is dependent on blocking the farnesylation of other proteins. Rheb (Ras homologue enriched in brain) is a farnesylated small GTPase that positively regulates mTOR (mammalian target of rapamycin) signaling. We found that Rheb and Rheb2 mRNA were elevated in various tumor cell lines relative to normal cells. Peptides derived from the carboxyl termini of human Rheb and Rheb2 are in vitro substrates for farnesyl transferase but not geranylgeranyl transferase-1. Rheb prenylation in cell culture was completely inhibited by SCH66336, indicating a lack of alternative prenylation. SCH66336 treatment also inhibited the phosphorylation of S6 ribosomal protein, a downstream target of Rheb and mTOR signaling. SCH66336 did not inhibit S6 phosphorylation in cells expressing Rheb-CSVL, a mutant construct of Rheb designed to be geranylgeranylated. Importantly, expression of Rheb-CSVL also abrogated SCH66336 enhancement of tamoxifen- and docetaxel-induced apoptosis in MCF-7 breast cancer cells and ES-2 ovarian cancer cells, respectively. Further, inhibition of Rheb signaling by rapamycin treatment, small interfering RNA, or dominant negative Rheb enhanced tamoxifen- and docetaxel-induced apoptosis, similar to FTI treatment. These studies demonstrated that Rheb is modified by farnesylation, is not a substrate for alternative prenylation, and plays a role in SCH66336 enhancement of the anti-tumor response to other chemotherapeutics.

Topics: Alkyl and Aryl Transferases; Animals; Antineoplastic Agents; Bridged-Ring Compounds; Caspases; Cell Line, Tumor; Farnesyltranstransferase; Humans; Monomeric GTP-Binding Proteins; Neoplasms; Neuropeptides; Phosphorylation; Piperidines; Protein Kinases; Protein Prenylation; Pyridines; Ras Homolog Enriched in Brain Protein; Recombinant Fusion Proteins; RNA, Messenger; Signal Transduction; Tamoxifen; Taxoids; TOR Serine-Threonine Kinases