Association of weight change with telotristat ethyl in the treatment of carcinoid syndrome

e15692

Background: In the Phase 3 TELESTAR study, the oral tryptophan hydroxylase inhibitor telotristat ethyl (TE) significantly reduced bowel movement (BM) frequency compared with placebo (pbo) over a 12-week Double-blind Treatment (DBT) period in patients with carcinoid syndrome (CS). Weight loss has previously been associated with uncontrolled CS and may result in reduced survival, so it is important to examine weight changes in patients with neuroendocrine tumors (NETs). Methods: We conducted an analysis, prespecified in the statistical analysis plan, of the incidence of weight change of ≥3% at Week 12 in TELESTAR. Patients with metastatic NETs, CS, and ≥4 BMs per day were randomly assigned to receive pbo, TE 250 mg 3x/day (tid), or TE 500 mg tid for 12 weeks, in addition to somatostatin analog therapy. Results: There were 45 patients in each group. Mean baseline age was 63.5 years, with 5.8 BMs/day and mean body mass index 24.87 kg/m2. Weight gain ≥3% at Week 12 was observed in 2/39 (5.1%), 7/41 (17.1%), and 13/40 (32.5%) patients on pbo, TE 250 tid, and TE 500 mg tid, respectively. The Cochrane–Armitage test for trend in weight gain incidence across groups yielded p = 0.0017. Among the 20 patients with a ≥3% weight gain on TE, 10 patients experienced a reduction of at least 30% in BM frequency at Week 12 (maximum reduction 75%). Weight loss ≥3% at Week 12 was observed in 5 (12.8%), 4 (9.8%), and 6 (15.0%) patients on pbo, TE 250 tid, and TE 500 mg tid. Adverse events of vomiting, decreased appetite, cachexia, and performance status decreased were reported during the DBT period among those with weight loss but not those with weight gain. Conclusions: The incidence of weight gain was dose-related on TE and was greater than that on pbo. It was possibly related to a reduction in diarrhea severity, and it may be a relevant aspect of TE efficacy among patients with functioning metastatic NETs. Clinical trial information: NCT01677910.

Hyperaccumulation of FAD-linked presenilin 1 variants in vivo

Mutations in the presenilin 1 (PS1) and presenilin 2 (PS2) genes can cause Alzheimer's disease in affected members of the majority of early-onset familial Alzheimer's disease (FAD) pedigrees. PS1 encodes an ubiquitously expressed, eight transmembrane protein. PS1 is endoproteolytically processed to an amino-terminal derivative (approximately 27-28 kDa) and a carboxy-terminal derivative (approximately 17-18 kDa). These polypeptides accumulate to saturable levels in the brains of transgenic mice, independent of the expression of PS1 holoprotein. We now document that, in the brains of transgenic mice, the absolute amounts of accumulated N- and C-terminal derivatives generated from the FAD-linked PS1 variants in which Glu replaces Ala at codon 246 (A246E) or Leu replaces Met at codon 146 (M146L) accumulate to a significantly higher degree (approximately 40-50%) than the fragments derived from wild-type PS1. Moreover, the FAD-linked deltaE9 PS1 variant, a polypeptide that is not subject to endoproteolytic cleavage in vivo, also accumulates in greater amounts than the fragments generated from wild-type human PS1. Thus, the metabolism of PS1 variants linked to FAD is fundamentally different from that of wild-type PS1 in vivo.

Modulators of carcinogenesis

For decades, it has been known that a number of different factors (e.g., species, metabolism, age, animal husbandry, diet) may exhibit a significant modulating effect on the process of carcinogenesis. Often, however, these modulators have been largely uncontrolled and thus have made uncertain the results of many carcinogenicity bioassays. Fortunately, current research into molecular carcinogenesis is beginning to provide methods, not only to understand the molecular basis of known modulators of carcinogenesis, previously described only in empirical terms, but also to allow genetic modulation of carcinogenesis in experimental systems. An expanding body of knowledge regarding the role of oncogenes and tumor suppressor genes in neoplastic events is leading to a better understanding of carcinogenic mechanisms and points to the use of transgenic animal species in carcinogenicity bioassays. The transgenic animal provides methods to examine the molecular basis of carcinogenesis in experimental systems in addition to enhancing the sensitivity of carcinogen identification and the biological specificity of chemical risk extrapolation.