The present invention provides peptides derived from the cytoplasmic region of protease-activated receptors 4 (PAR4) as well as analogs and cyclic analogs, such as backbone cyclic analogs, of these peptides. Pharmaceutical compositions comprising said peptides, analog, cyclic analogs and well as conjugates thereof are provides as well. The peptides, analogs and conjugates of the present invention and pharmaceutical composition comprising thereof have several uses including treating cancer and inhibiting interactions between PARs and protein comprising PH-domain.