SEATTLEMelanoma patients with specific human leukocyte antigen
(HLA) phenotypes may respond better to an investigational therapeutic
vaccine known as Melacine than those without the phenotype, Vernon
Sondak, MD, reported for the Southwest Oncology Group (SWOG) at the
Society of Biological Therapy annual meeting.
Melacine, under development by Corixa Corporation (Seattle), consists
of lysed cells from two human melanoma cell lines combined with
Corixas proprietary Detox adjuvant. Detox adjuvant includes
monophosphoryl lipid A and mycobacterial cell wall skeleton, both of
which activate the human immune system in the context of vaccination.
Dr. Sondak previously reported results of the phase III trial of 689
stage II melanoma patients randomized to adjuvant immunotherapy with
Melacine or observation following surgical excision of their primary
Although analysis of the eligible population (600 patients) showed no
significant difference in disease-free survival between the two
groups, intent-to-treat analysis showed significantly longer
disease-free survival for patients treated with Melacine (P =
.04). The vaccine was particularly beneficial in patients with
thinner tumors (less than 3 mm), he said.
Expression of five HLA genes (HLA-A2, A28, B44, B45, and C3) was
determined in 80% of the 689 study patients, he said. The new
analysis found that disease-free survival was significantly better in
vaccinated patients who expressed two or more of the five
prospectively defined HLA alleles (P = .0001), compared with
patients with the same HLA phenotype who were not vaccinated after surgery.
The effect was predominantly related to expression of HLA-A2, which
was found in 46% of the study population, and HLA-C3 (29%). The
investigators speculate that certain HLA alleles may be critical to
the binding and presentation of melanoma antigens in the vaccine.