Multiple myeloma is a form of cancer that affects plasma cells, which are mainly found in the bone marrow. Targeted therapy is a type of treatment for multiple myeloma.

Multiple myeloma occurs when cancerous plasma cells grow out of control. According to the American Cancer Society, just under 35,000 people in the U.S. will get a multiple myeloma diagnosis in 2021.

In this article, we look at the definition, types, effectiveness, and side effects of targeted therapy.

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Multiple myeloma is a type of cancer. It affects the plasma cells in the bone marrow. It happens when plasma cells grow out of control.

The American Cancer Society explains that other conditions can also affect plasma cells, but multiple myeloma has the following features:

  • Low blood count: This can cause anemia, abnormal bleeding, and problems fighting off infections.
  • Bone and calcium issues: This may increase a person’s risk for bone breaks.
  • Higher rate of infections: The body cannot fight infections off with damaged plasma cells.
  • Kidney problems: This happens because of the production of kidney-harming antibodies.

Symptoms of multiple myeloma may include:

  • bone pain, often in the skull, hips, or back
  • weak or broken bones
  • fatigue
  • shortness of breath
  • dizziness
  • extreme thirst
  • increased urine production
  • severe constipation
  • loss of appetite
  • weakness
  • numbness, usually in the legs

Aside from targeted therapy, other treatments for multiple myeloma include:

  • chemotherapy
  • corticosteroids
  • bisphosphonates, to help with bone pain and weakness

Targeted therapy is a type of cancer treatment. It specifically targets molecules that support cancer growth.

Because they have specific targets, these therapies generally produce fewer effects on nearby noncancerous cells.

There are two main types of targeted therapy for multiple myeloma. They are:

Antibodies

Monoclonal antibodies are intravenous (IV) drugs that attach to cancer cell proteins. These include daratumumab (Darzalex) and elotuzumab (Empliciti).

Doctors use both these treatments in combination with other drugs such as Revlimid and dexamethasone.

In 2020, the FDA also approved the use of monoclonal antibody isatuximab-irfc (Sarclisa) for multiple myeloma treatment. This medication is similar daratumumab.

Small molecule inhibitors

People can take small molecule inhibitors intravenously or orally. Because of their small size, these inhibitors can travel inside cells to target cancer. They include proteasome inhibitors and HDAC inhibitors.

Proteasome inhibitors impact a cell’s ability to dispose of waste. As waste builds up within a cell, the cell cannot function properly. This causes cancer cells to die. The following proteasome inhibitors have FDA approval:

  • bortezomib (Velcade)
  • carfilzomib (Kyprolis)
  • ixazomib (Ninlaro)

HDAC inhibitors limit the production of a specific protein called histone deacetylase (HDAC), which allows for rapid growth and spread of cancer cells. Panobinostat (Farydak) is the only HDAC inhibitor that currently has FDA approval.

The FDA also recently approved a drug called belantamab mafodotin-blmf (Blenrep). It is a type of immunotherapy for multiple myeloma called BCMA-targeted therapy.

According to research in the journal Frontiers in Immunology, targeted therapies such as proteasome inhibitors and monoclonal antibodies have greatly increased survival rates in people with multiple myeloma.

There is still no cure for this type of cancer, but targeted therapies may help prolong a person’s life. This is especially true when a person responds poorly to other treatments.

While people often develop resistance to targeted therapies, newer immunomodulating drugs like Blenrep may be a promising option in cases where a person develops a resistance to other treatments.

In addition, the National Cancer Institute states that using targeted therapies in combination with other traditional cancer treatments may be more effective than using them alone.

Research into immunotherapies like Blenrep is ongoing. However, according to the FDA, 31% of participants in the Blenrep trial on a lower dose responded positively to the treatment, while 34% receiving a higher dose responded favorably. In the first group, 73% of those with a positive response saw effects lasting more than 6 months.

Because of this result, the FDA gave the drug accelerated approval. However, the approval may not be permanent and the drug’s long-term future depends results of additional trials.

According to the National Cancer Institute, side effects of targeted cancer therapies may include:

  • diarrhea
  • liver problems
  • skin issues including rash, dry skin, and hair color changes
  • high blood pressure
  • blood clotting issues and slow wound healing

Although the FDA gave benlatamad mafodotin-blmf accelerated approval, at least 20% of participants experienced adverse reactions such as:

  • vision issues
  • nausea
  • fever
  • fatigue

There is no cure for multiple myeloma. However, research into treatments has helped prolong the lives of people living with the condition.

Different types of targeted therapy may help people with multiple myeloma live longer. However, although targeted therapies show promise, they cannot cure this type of cancer. They also have many potential side effects.

People should discuss their treatment options with their oncology team. A cancer specialist can help a person weigh the pros and cons of different types of treatments.

Often, doctors will recommend a treatment plan that combines conventional cancer treatment, such as chemotherapy, with targeted therapy to maximize treatment effectiveness.