Reciprocal effects of mTOR inhibitors on pro-survival proteins dictate therapeutic responses in tuberous sclerosis complex

Inhibition of NAMPT as a therapeutic strategy to suppress tumor growth in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, progressive lung disease driven by mutations in the TSC1 or TSC2 genes, leading to constitutive mTORC1 activation and uncontrolled cell proliferation. Current therapies, like rapamycin effectively stabilize disease progression but mainly exert cytostatic effects and promote autophagy, a survival mechanism in LAM cells. These limitations highlight the need for the development of innovative therapies to achieve more effective and lasting results. To explore alternative therapeutic targets, we investigated the role of nicotinamide phosphoribosyltransferase (NAMPT), a key regulator of NAD+ biosynthesis, in LAM and TSC2-deficient cells using a potent inhibitor, FK866. Our study demonstrates that FK866 depletes NAD+ levels in these cells, exerting a dual effect by activating AMPK and subsequently inhibiting mTORC1 signaling while suppressing autophagy. Unlike rapamycin, FK866 does not induce compensatory Akt activation, significantly inhibits LAM cell proliferation and induces apoptosis. Additionally, using an in vivo chicken egg chorioallantoic membrane (CAM) model, we showed that FK866 treatment significantly reduces LAM tumor growth compared to controls suggesting that NAMPT inhibition disrupts metabolic and survival pathways critical for TSC2-deficient cell viability and tumor progression. Our results establish NAMPT as a promising therapeutic target for LAM, offering a two-prong strategy to suppress tumor growth and enhance apoptosis, providing an alternative to current mTOR-based therapies.

A phase 1 study of the combination of BH3-mimetic, navitoclax, and mTORC1/2 inhibitor, vistusertib, in patients with advanced solid tumors

PURPOSE

To determine the, safety, tolerability and recommended phase 2 dosing of the combination of navitoclax, a dual Bcl-2/xL inhibitor, and vistusertib, a TORC1/2 inhibitor.

METHODS

Patients with advanced solid tumors received navitoclax plus vistusertib following a 3 + 3 dose escalation design. To mitigate thrombocytopenia, a known toxicity of navitoclax, all patients received lead-in dosing of navitoclax alone at 150 mg orally daily for a minimum of 7 days. In addition to safety and tolerability, pharmacokinetics of navitoclax and vistusertib were evaluated.

RESULTS

14 patients received combination treatment which was well-tolerated at dose level 1 (navitoclax 150 mg orally daily plus vistusertib 35 mg orally twice daily). The main dose-limiting toxicity, grade 3 serum aminotransferase elevation, occurred in two of five patients at dose level 2 (navitoclax 250 mg orally daily plus vistusertib 35 mg orally twice daily). Navitoclax and vistusertib exposures appeared consistent with levels reported in prior studies of each agent. No responses were observed among the 8 response evaluable patients.

CONCLUSIONS

A tolerable dose of navitoclax at 150 mg orally daily plus vistusertib at 35 mg orally twice daily was identified in patients with advanced solid tumors and established as the recommended phase 2 dose (RP2D). Further efficacy assessment of this combination, in a planned phase 2 expansion in patients with relapsed small cell lung cancer, was terminated due to discontinuation of vistusertib.

TRIAL REGISTRATION

NCT03366103 (First posted December 8, 2017).

Fatty acid synthase (FASN) signalome: A molecular guide for precision oncology

The initial excitement generated more than two decades ago by the discovery of drugs targeting fatty acid synthase (FASN)-catalyzed de novo lipogenesis for cancer therapy was short-lived. However, the advent of the first clinical-grade FASN inhibitor (TVB-2640; denifanstat), which is currently being studied in various phase II trials, and the exciting advances in understanding the FASN signalome are fueling a renewed interest in FASN-targeted strategies for the treatment and prevention of cancer. Here, we provide a detailed overview of how FASN can drive phenotypic plasticity and cell fate decisions, mitochondrial regulation of cell death, immune escape and organ-specific metastatic potential. We then present a variety of FASN-targeted therapeutic approaches that address the major challenges facing FASN therapy. These include limitations of current FASN inhibitors and the lack of precision tools to maximize the therapeutic potential of FASN inhibitors in the clinic. Rethinking the role of FASN as a signal transducer in cancer pathogenesis may provide molecularly driven strategies to optimize FASN as a long-awaited target for cancer therapeutics.