Duvelisib

Duvelisib acts as a strong reversible inhibitor of the isoform gamma and delta of the phosphoinositide3-kinase (PI3K). PI3K plays a very important role in innate and adaptative immunity and the inhibition of the form delta and gamma has been very important for the suppression of immunity.

The activity of PI3K gamma and delta is restricted to hematopoietic cells and it is necessary for normal B cell development. In lymphomas, the activation of PI3K is enlarged to promote unlimited growth and survival. Hence, inhibition of PI3K can provide an inhibition of the signaling from BCR, inhibition of a cytokine signaling from the microenvironment and enhancement of anti-tumor immunity. The specific mechanism of this PI3K inhibitors are further described as follows:

-BCR activates signaling pathways after antigen engagement and it is also critical for the physiologic life of the lymphocytes and neoplastic lymphomas. In CLL, BCR reacts to auto- and exo-antigens to promote clonal expansion. This sustained presence of BCR activates delta PI3K producing a pro-survival pathway of the neoplastic cells which already present a higher activity of PI3K. Thus, the blockade of PI3K will limit the activity of BCR and the driven physiology of the lymphoma.

-The inhibition of PI3K can also inhibit paracrine and autocrine pro-survival signals mediated by adhesion molecules, chemokines and soluble factors. This activity is attained due to the fact that several downstream signals convey on PI3K.

-It has been reported that inactivation of PI3K produces a significant resistance to tumorigenesis. This data suggests that inhibition of PI3K can facilitate recognition and elimination of tumor cells.

In summary, duvelisib inhibits the isoform delta of PI3K which is necessary for cell proliferation and survival and the isoform gamma which is critical for cytokine signaling and the pro-inflammatory response.