The limitations of currently available rapalogs have led to new approaches to mTOR targeting. Studies suggest that mTOR inhibitors may have anticancer activity in many cancer types, such as RCC, neuroendocrine tumors, breast cancer, hepatocellular carcinoma, sarcoma, and large B-cell lymphoma.
One major limitation for the development of mTOR inhibition therapy is that biomarkers are not presently available to predict which patient will respond to them.  A better understanding of the molecular mechanisms that are involved in the response of cancer cells to mTOR inhibitors are still required so this can be possible.
A way to overcome the resistance and improve efficacy of mTOR targeting agents may be with stratification of patients and selection of drug combination therapies.  This may lead to a more effective and personalized cancer therapy. Although further research is needed, mTOR targeting still remains an attractive and promising therapeutic option for the treatment of cancer.