Let's learn about Antibody-Drug Conjugates (ADCs) - the 'magic bullet' that finds cancer cells and delivers medicine?

When we say "cancer", one of the words that immediately comes to mind is "chemotherapy". Many people are afraid of this treatment because it causes hair loss and is difficult for the body. However, with the advancement of medical science, new methods have been introduced to the world that can target only cancer cells and greatly reduce the damage to healthy cells. Today, we are going to talk about a treatment method that has made a big breakthrough in the world of cancer treatment, and works like a 'magic bullet'. That is Antibody-Drug Conjugates, or ADCs as we call them for short.

Simply put, what is this Antibody-Drug Conjugate (ADC)?

Imagine, you need to deliver a parcel to just one person in a crowded place. How much easier would it be to find that person and deliver the parcel instead of distributing it to everyone? That's what this ADC does.

ADC is a combination of three parts. To be precise, it is like a 'smart bomb' made with technology.

1. Antibody: This is our 'identification agent'. There are special proteins (we call these ``tumor antigens'') that are only on the surface of cancer cells. This antibody is made to go and stick to the proteins on those cancer cells. It's like a key that fits into its corresponding lock. Since healthy cells don't have these proteins, this antibody doesn't stick to them. Because these are specially made in laboratories, we also call them ``Monoclonal Antibody''.

2. Chemotherapy drug: This is what's inside that package. It uses a much stronger anti-cancer drug than what's given in regular chemotherapy. Because it goes directly into the cancer cell, it can give a powerful drug without harming the healthy cells outside.

3. Linker: This is the 'gum' that holds the spy (Antibody) and the bomb (Chemo drug) together. The function of this linker is to keep the drug from being released until the antibody finds the cancer cell and enters it. Only after the cancer cell has entered does this linker break, releasing the drug.

How does this 'biological missile' work?

This process is very interesting. Let's see what happens step by step.

• Step 1: The ADC drug is injected into the patient's vein through a saline solution.
• Step 2: This drug travels throughout the body through the blood. However, as it travels, the antibody part acts like a GPS, finding where the cancer cells are.
• Step 3: Once a cancer cell is found, the antibody goes and 'locks' on a specific protein (antigen) on the surface of that cell.
• Step 4: Once locked in like this, the cancer cell thinks this is something it wants. So it pulls this entire ADC package inside itself.
• Step 5: Once inside the cancer cell, the enzymes inside break down that 'linker'.
• Step 6: As the linker breaks, the highly potent chemotherapy drug that was bound to it is released inside the cancer cell.
• Step 7: Due to the strength of this medicine, the cancer cell is destroyed from within.

What types of cancer are treated with ADC?

ADC is not a treatment for all types of cancer. Currently, doctors consider this treatment for certain types of cancer, especially when other treatments have failed (`(refractory cancer)`), the cancer has come back (`(recur)`), or has spread to other parts of the body (`(metastasize)`).

Let's explain this further in the table below.

Several ADC drugs used in the world

There are already more than a dozen ADC drugs approved by agencies such as the FDA in the United States. Some examples are:

• Brentuximab vedotin (Adcetris®): Used for blood cancers such as Hodgkin lymphoma.
• Trastuzumab emtansine (Kadcyla®): Used for HER2-positive breast cancer that has spread throughout the body.
• Sacituzumab govitecan (Trodelvy®): Used for triple-negative breast cancer and bladder cancer.

Are there no side effects of this treatment?

Although it is said that "harm to healthy cells is minimal", this does not mean that there are no side effects of this treatment. However, compared to regular chemotherapy, these are often manageable. The side effects that occur can vary from patient to patient, depending on the type of cancer, its stage, and the patient's overall health.

Your oncology team will monitor you closely throughout your treatment. If any side effects occur, they will provide you with immediate treatment.

Common side effects:

• Fatigue
• Nausea and vomiting
• Anemia
• Leukopenia (low white blood cell count)
• Low blood platelet count (`(Thrombocytopenia)`)
• Anorexia
• Constipation or diarrhea
• Headache, fever
• Peripheral neuropathy - numbness and tingling in the limbs
• Skin rash

It is very important to inform your doctor immediately about any of these things, even if they are minor.

Can we have hope for this treatment?

Yes, absolutely. ADC is a treatment that has brought new hope to many cancer patients. Studies have shown that patients who receive ADC treatment live longer than those who receive standard chemotherapy alone.

And this field is developing very rapidly. At the moment, more than 100 clinical trials are underway around the world. Scientists are trying to develop ADCs that are more effective and have fewer side effects for more types of cancer. Therefore, we can hope that in the future, we will be able to obtain this 'magic bullet' treatment for many more types of cancer.

Cancer treatment, ADC, Antibody-Drug Conjugates, Chemotherapy, Targeted therapy, Cancer side effects, Monoclonal antibody