The present invention describe nanocomplexes also called auto-assembling nanoparticles comprising biphosphonates, lipid nanovectors and inorganic nanovectors.In particular the invention describes zoledronic acid complexed with calcium phosphate base nanoparticles; said particles in their turn mixed with lipidic particles e.g. liposomes.Said nanocomplexes are useful, and showed to be efficient in vivo, as pharmaceutical formulations of biphosphonates for the treatment or prevention of tumor growth and/or metastasis. Tumors can be solids and/or haematological such as prostate, lung, head/neck, colon, liver, breast, pancreas, kidneys, bladder, male and female urogenital tract, bones, multiple myeloma, primitive and secondary tumors of the central nervous system and lymphomas.