Trastuzumab: Uses, Interactions, Mechanism of Action

What Is Trastuzumab?

Trastuzumab is a type of monoclonal antibody, which means it is designed to specifically target and attach to proteins or receptors on the surface of cancer cells. It was first approved by the FDA in 1998 and has since become a standard treatment for HER2-positive breast cancer.

HER2, or human epidermal growth factor receptor 2, is a protein that promotes the growth of cancer cells. In some breast cancer patients, HER2 is overexpressed, meaning there is an excessive amount of this protein present. This overexpression can lead to aggressive tumour growth. The trastuzumab drug was created to specifically bind to HER2 receptors on the surface of these cancer cells, helping to inhibit their growth and division.

While trastuzumab drug is primarily used to treat HER2-positive breast cancer, it has also been approved for other cancers, such as gastric (stomach) cancers, where HER2 plays a role in the development of the disease.

Uses of Trastuzumab

1. HER2-Positive Breast Cancer
   The primary use of trastuzumab is for treating HER2-positive breast cancer, which accounts for about 20% of all breast cancers. This drug is used in both early-stage and metastatic (advanced) breast cancer. When used in combination with other chemotherapy agents, trastuzumab has been shown to significantly improve outcomes for patients, helping to reduce the risk of cancer recurrence.
2. HER2-Positive Gastric Cancer
   Trastuzumab is also used to treat HER2-positive gastric or gastroesophageal junction cancer. While less common than its breast cancer use, it can be a valuable part of treatment for patients with advanced stomach cancer that overexpressed HER2. In combination with chemotherapy, the trastuzumab drug can slow the progression of the disease.
3. Adjuvant and Neoadjuvant Therapy
   In addition to treating metastatic cancer, trastuzumab can be used as an adjuvant (post-surgery) or neoadjuvant (pre-surgery) therapy. This helps reduce the likelihood of cancer returning after surgery by targeting any remaining HER2-positive cancer cells.

How Trastuzumab Works: The Mechanism of Action

The mechanism of action of the trastuzumab drug is fascinating and highlights the advancements in precision medicine. Rather than attacking all rapidly dividing cells like traditional chemotherapy, trastuzumab works in a more targeted way:

• Targeting HER2 Receptors: Trastuzumab specifically binds to the HER2 receptors on the surface of cancer cells. By attaching itself to these receptors, the drug blocks the signals that tell the cancer cells to grow and divide uncontrollably.
• Activating the Immune System: Once trastuzumab has bound to the HER2 receptors, it also marks the cancer cells for destruction by the immune system. This is known as antibody-dependent cellular cytotoxicity (ADCC), where immune cells recognise the trastuzumab-bound cancer cells and attack them directly.
• Preventing Cell Repair: In addition to blocking growth signals, the trastuzumab drug can prevent the cancer cells from repairing themselves, making them more susceptible to damage from chemotherapy or radiation.

These targeted actions make trastuzumab a highly effective treatment for HER2-positive cancers, with fewer side effects than traditional chemotherapy. However, like all drugs, it does come with some potential risks and interactions.

Interactions and Side Effects of Trastuzumab

While trastuzumab is a powerful and effective drug, it’s essential for patients and healthcare providers to be aware of potential interactions and side effects.

Drug Interactions

Patients undergoing trastuzumab therapy may also be receiving other medications, particularly chemotherapy agents. It’s crucial to ensure that these drugs are compatible. While there are no major known drug interactions specific to trastuzumab, patients should always inform their healthcare providers of all medications they are taking, including over-the-counter drugs and supplements.

In some cases, the combination of the trastuzumab drug with chemotherapy can increase the risk of certain side effects, such as heart-related issues. This makes regular monitoring by a healthcare professional critical.

Side Effects

Like all medications, trastuzumab drugs can cause side effects, although not everyone will experience them. The most common side effects include:

• Infusion Reactions: Some patients may experience reactions during the infusion of the drug, such as fever, chills, or nausea. These reactions are typically mild but should be monitored closely.
• Heart Problems: One of the more serious potential side effects of trastuzumab is its impact on heart function. It can lead to a condition known as cardiomyopathy, which weakens the heart muscle. Patients undergoing trastuzumab treatment often have their heart function monitored with regular echocardiograms or other heart tests.
• Fatigue and Weakness: Many patients report feeling tired or weak during treatment, which is common with most cancer therapies. It’s important to listen to your body and rest when needed.
• Diarrhoea: Gastrointestinal side effects like diarrhoea can occur, but these are typically manageable with supportive care.

Patients should always discuss potential side effects and any concerning symptoms with their healthcare provider to manage them effectively and ensure the best outcome.

The Future of Trastuzumab and Precision Medicine

The trastuzumab drug represents an important step forward in the field of targeted cancer therapies. Its ability to specifically target HER2-positive cancer cells without causing widespread damage to healthy cells has improved the quality of life for many patients. However, researchers are continuing to develop new formulations and combinations of trastuzumab with other therapies to make it even more effective.

For example, there are now newer versions of trastuzumab, such as trastuzumab emtansine, which combine the targeted antibody with a chemotherapy agent, delivering a one-two punch to cancer cells while minimising side effects. Ongoing research aims to find even better ways to use trastuzumab in combination with other treatments to further improve survival rates for HER2-positive cancers.

Conclusion

The trastuzumab drug has revolutionised the treatment of HER2-positive cancers, providing a more targeted and effective approach compared to traditional chemotherapy. By specifically attacking HER2 receptors and enlisting the body’s immune system, trastuzumab offers hope to patients with breast and gastric cancers that might otherwise be more difficult to treat.

As with any medication, it’s important to be aware of potential interactions and side effects, but under the careful guidance of a healthcare provider, the trastuzumab drug remains one of the most powerful tools in the fight against cancer. Through ongoing research and continued advancements in precision medicine, trastuzumab will likely remain at the forefront of cancer treatment for years to come.