Experimental Melanoma Vaccine May Shrink Late-Stage Tumors
Researchers from MD Anderson Cancer Center in Houston, Texas, and the Indiana University Health Goshen Center for Cancer Care in Goshen have discovered that gp100:209-217 (200M), an experimental melanoma vaccine also known as the gp100 peptide vaccine, in combination with interleukin-2 (IL2), an immune-stimulating drug, may shrink tumors and prevent the progression of late-stage melanoma. Their report was published yesterday in the New England Journal of Medicine.
The randomized phase III trial enrolled 185 patients at 21 centers. To be eligible to participate in the study, patients needed to have stage IV or locally advanced stage III cutaneous melanoma, expression of the HLA*A0201 binding peptide, no brain metastases, and the ability to receive high-dose IL2 therapy. All patients received the high-dose IL2 therapy (720,000 IU/kg per dose), but only 91 patients were randomly assigned to receive gp100 peptide vaccine. The gp100 peptide vaccine works by stimulating T cells, which then attack antigens on the surface of cancer cells.
The gp100 vaccine/IL2 group showed significant improvement (ie, cancer tumors shrunk ≥50%) over the IL2-only group in overall clinical response (16% vs 6%). Patients in the gp100/IL2 group also had longer progression-free survival (PFS) compared with those in the IL2-only group (2.2 months vs 1.6 months). Median overall survival was also longer in the gp100/IL2 group versus the IL2-only group (17.8 months vs 11.1 months).
A study researcher, Douglas J. Schwartzentruber, MD, of the Indiana University Health Goshen Center for Cancer Care, acknowledged in a published report that these “numbers are small, if you look at the absolute numbers in terms of the benefit.” However, he pointed out that vaccines for melanoma are relatively new and that ipilimumab (Yervoy) was only just approved by the FDA in March for the treatment of melanoma.
The study’s primary end point was clinical response. Secondary end points were toxic effects and PFS.