Findings from a recent Phase 2 clinical study of a multiple myeloma vaccine indicate that the vaccine deepens responses following autologous stem cell transplantation.

Almost half of the patients in the trial achieved a complete response and almost another third achieved a very good partial response after vaccination.

The investigators state that these response rates compare favorably to initial therapy with Revlimid (lenalidomide) or Velcade (bortezomib) followed by stem cell transplantation.

Based on their results, the researchers believe the vaccine used in this trial may be beneficial for patients undergoing autologous stem cell transplantation. They state that another study is being planned that will compare the efficacy of stem cell transplantation with and without the addition of this vaccine.

In addition, they recommend further study of this vaccine in combination with Revlimid maintenance therapy to assess whether the combination synergistically extends overall survival.

Background

Therapeutic vaccination is a promising treatment option for multiple myeloma. It works by activating the immune system to recognize tumor cells as “foreign,” triggering their destruction.

However, developing effective vaccines is a challenge, since they must elicit a strong immune response and target only cancer cells.

The current clinical trial investigated a cell-based vaccine, which involves using cells isolated from the patient’s bone marrow. Specifically, the vaccine is personalized for each patient and is made up of their myeloma tumor cells fused together with their dendritic cells, a type of immune cell that helps activate the immune system.

Previous results from a Phase 1 clinical trial demonstrated that this type of vaccination can induce an immune response and is well tolerated (see related Beacon news).

Study Design

The investigators enrolled 36 newly diagnosed transplant-eligible patients with a median age of 58 years.

Two-thirds of the patients received three vaccinations at 4-week intervals following stem cell transplantation using their own stem cells. The other third was vaccinated once before stem cell transplantation, and then subsequently received three vaccinations at 4-week intervals following transplantation.

Prior to stem cell transplantation, the patients had received a median of two treatment regimens to reduce the number of myeloma cells in their bone marrow.  In particular, 67 percent had received a Velcade-based regimen, 31 percent thalidomide (Thalomid), and 19 percent Revlimid; additionally, 31 percent were treated with Revlimid, Velcade, and dexamethasone (Decadron) combination therapy.

Results

Overall, 47 percent of patients achieved a complete response and 31 percent achieved a very good partial response.

The investigators note that 31 percent of the patients achieved a complete response soon after the transplant, while the remaining 17 percent achieved a complete response more than 100 days after receiving all of their vaccines.

According to the researchers, this delayed deepening of responses indicates the vaccine was effective against residual disease following initial therapy with novel agents and transplantation.

The researchers also found that the amount of immune cells that fight myeloma cells increased tenfold after vaccination.

After a median follow-up of 46 months, the two-year progression-free survival rate was 57 percent.

According to the investigators, the vaccine was well tolerated. All side effects were mild or moderate. The most common side effect was redness and itching at the site of injection, followed by pain in the muscle or joints.

For more information, please refer to the study in the journal Clinical Cancer Research (abstract).