Imbruvica, by Pharmacyclics (PCYC-$135.20), received accelerated approval for MCL based on a study
where 111 participants were given Imbruvica daily until their disease
progressed or side effects became intolerable. Results showed nearly 66 percent
of participants had their cancer shrink or disappear after treatment (overall
response rate).
Imbruvica blocks the function of Bruton’s tyrosine kinase (BTK), a
key signaling protein of the B-cell receptor signaling complexes that stimulate
malignant B-cells to grow and divide uncontrollably.
MCL affects the white blood cells called lymphocytes found in the
“mantle zone” of a lymph node. A rare form of NHL, and most prevalent in older
adults (mean age, 68), MCL is an aggressive B-cell malignancy affecting about
6% of the 72,000 new cases of NHL diagnosed in the U.S. annually.
To date, first-line treatment has usually consisted of Roche’s
monoclonal antibody Rituxan (rituximab) – which is directed against the CD20
antigen found on Beta lymphocytes – combined with a multi-agent chemotherapy
regimen, most often CHOP (cyclophosphamide, doxorubicin, vincristine, and
prednisone).
Given the complex pathophysiology of the disease (multiple
cell-signaling division triggers), combined with a late-stage diagnosis
typically discovered after the spread to the GI tract and bone marrow, MCL is
characterized by short median survival times (3 – 5 years).