This article explains, in a patient-friendly manner, the different types of anti-cancer drugs as more and more are launched, from immunotherapy, to chemotherapy, to mono-clonal antibodies, bisphosphonates, hormone therapies and even old drugs never intended for use in cancer treatment but repurposed to help out.
When we hear about cancer drugs, most of us immediately think of chemotherapy. But Pharmaceutical companies would like to consign the word chemotherapy to the past and with it the fear, the bad press, the risks and the poor performance. Life must move on. (Original article by Dr. Nicola Hembury; updated July 2019)
Complementary and Integrative Medicine in cancer
Now we have a new generation of drugs - Immunotherapy. It's an exciting progression. And drugs launched targeting a single protein issue or a genetic flaw which were called Biologics are now asking to be called immunotherapy drugs too. Then there are highly functional drugs from hormone therapies to substances that can strengthen your bones (bisphosphonates). And finally, oncologists are now looking into drugs created for other illnesses, like metformin for diabetes, that can be repurposed to help fight cancer. In future, you may still receive chemotherapy drugs, but you may receive hormone therapy, bisphosphonates, immunotherapy and even a beta-blocker as part of your personal Complementary and Integrative Medicine programme for your particular cancer.
Increasing use of personalised and targeted drugs
"There is also a trend in cancer drug prescribing toward personalising treatments," says Dr Nicola Hembry, Director of Integrated Health Screening and specialist in environmental and nutritional medicine. "With the advent of chemo-sensitivity testing you can even discover before you begin whether the drug offered is going to work well with your type of cancer."
Other tests on the cancer cells themselves also reveal what type of drug will work best with the way your cancer cells are operating. Specific drugs may be used if you have a BRCA1 mutation, for example; or an EGFR wild type mutation.Testing will also protect you - for example, in the use of the drug 5FU which has been found to be life-threatening for people who have a deficiency in an enzyme called DPD which makes your body unable to detoxify it. This is not yet tested for in the UK.
Side effects of newer drugs
Unfortunately, the promise of less side-effects with newer drugs does not seem to be materialising. As drugs become more specific and work on just the 15-20% of people with a specific genetic issue, patients had hoped for better results and less side-effects. New immunotherapy drugs seem to completely flatten the microbiome causing fatigue and infection, even death. As Professor David Colquhoun, an eminent pharmacologist said on question time on TV in the UK, "The problem is that many of these new drugs just don't work very well." He went on to talk about their enormous costs and blamed the marketing and sales budgets.
Different types of anti-cancer drugs
1. General Chemotherapy Drugs
These can be referred to as alkylating agents, anti-neoplastics, anti-metabolites and although they might have different ways of doing it, they all act on the DNA to stop cancer cells reproducing. The reason they also have side-effects is that they cannot differentiate between the cancer cells and normal cells. Some, like 5-FU were approved as long ago as 1956. You might also hear of chemotherapy drugs being referred to as 'cytotoxic' which means they are toxic to cells; all cells.
2. Steroids
These generally have three purposes. First, they enhance a sense of wellness in people undergoing treatment boosting appetite, for instance. Second, they have some active benefits, for example with pleural effusion (fluid in the lung) and swelling in the brain around brain tumours where the drug dexamethosone is likely to be used. Third, they reduce the interactive effects on you of multiple chemotherapy drugs. A drug commonly used here is prednisolone.
3. Bisphosphonates
These are drugs which can help protect the bones against some of effects of cancer such as pain or weakness and are sometimes described as bone strengthening. They also raise the level of calcium in the blood. Drugs in this category include Clondronate (Bonefos), Ibandronic acid (Bondranat), Pamidronate and Zoledronic acid.
4. Hormone Therapies
Cancer cells need hormones to grow, so there are a variety of drugs available to act on the production of hormones. In women the cancers that are hormone sensitive include breast, ovarian and uterine, while for men prostate cancer is hormone sensitive. Hormones are also thought to be implicated in other cancers such as melanoma.
Oestrogen and progesterone both affect some breast cancers. Tests will be done to find out whether you are sensitive to either of these. Hormone therapy will then be prescribed to stop the hormones getting to the breast cancer cells thus starving them of something they need to grow.
Aromatase inhibitors are one particular kind of hormone therapy. Aromatase inhibitors are a type of hormone therapy which blocks the growth of tumours by blocking the amount of oestrogen in the body. Although oestrogen is made in the ovaries, aromatase inhibitors don’t stop the ovaries from producing it, but they can block other tissues from making it. Thus, they are most often used in women who have reached menopause.
They include anastrozole (Arimidex); exemestane (Aromasin) and Letrozole (Femara). There is a risk of bone loss with these treatments, but other drugs can be taken to mitigate this. Zoledronic Acid has been shown to be helpful with this.
Tamoxifen is another drug which prevents the growth of oestrogen-sensitive breast tumours but has a different action whereby it blocks the tumour’s ability to use the oestrogen.
A third type of hormone treatment focuses on the hormones made in the pituitary gland. This is a treatment used for women who have not yet had a menopause. Goserelin (Zoladex) and leuprorelin are examples of this. For men, goserelin for prostate cancer, leuprorelin and triptorelin prevent the testicles from making testosterone.
Anti-androgens are another type of hormone treatment for prostate cancer and include biculatamide (Casodex), cyproterone acetate (cyprostat) and flutamide (Drogenil).
5. Biological therapies / Immunotherapy
Biological therapies use substances that naturally occur in the body to destroy cancer cells. There are various different types described below all with different mechanisms,
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Monoclonal antibodies :-Our bodies are naturally designed to fight infection through the production of antibodies which work with the immune system to recognise an infection if we are exposed to it again and help the body deal with it (hence they are used to make vaccines). Monoclonal antibodies are made from a single cell and work by recognising the protein on the surface of the cancer cell and then locking onto it, which then triggers the immune system to attack and destroying the cancer cell. Drugs that end in MAB are monoclonal antibodies that target the protein receptors on the cell. These would include alemtuzumab or rituximab. Other monoclonal antibodies which act by stopping cancer cells from taking up proteins and they would include trastuzumab (Herceptin); bevacizumab (Avastin) and cetuximab (Erbitux).
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Another type of biological therapy is the cancer growth blockers that block or inhibit the enzyme tyrosine kinase. These are known as tyrosine kinase inhibitors (TKIs). Proteasome / Protease inhibitors are another type of growth blocker.
Drugs that end in NIB act within the cell blocking the messenger activity of the tyrosine kinase which is part of the signalling process within the cell. When this is blocked the cells can’t divide and grow. Examples include Erlotinib (Tarceva), imatinib (Gleevec), gefinitib (Iressa), dasatinib (Sprycel) and sunitinib (Sutent).
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Proteasome Inhibitors (PIs) work on the proteasomes that are found within all cells with the role of breaking down proteins. This makes them essential in a host of normal cellular processes like gene expression and message carrying. Research has shown that inhibiting proteasome activity in cancer cells seems to block cell proliferation and increase apoptosis or cell death. Currently bortezomib, which is usually administered intravenously, is approved in the USA for patients with resistant or relapsed myeloma. Hospitals such as Sloan-Kettering in New York have high hopes for PI drugs and are investigating Carfilzomib.
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Interferon and interleukin are natural substances that are part of our immune system. They are now manufactured in large amounts and one of their functions is to stimulate the immune system to produce killer cells which will take on the cancer cells. Aldesleukin comes into this class of drug.
6. Immunotherapy
These drugs have been described as the fourth leg of the orthodox medicine chair, along with surgery, chemotherapy and radiotherapy. Unfortunately, most of the monoclonal antibody drugs have jumped on the Immunotherapy bandwagon, and now also claim to be immunotherapy drugs. They are not.
Typically, immunotherapy drugs started with Nivolumab and ipilimumab, Unfortunately, good results only occur in approximately 17% of patients. Sometimes oncologists now use two drugs together. We now have others performing better, like Pembrolizumab. There are now CAR-T immunotherapy drugs tailored to your immune system. We have a complete review of immunotherapy.
Go to: Overview of immunotherapy and immunotherapy drugs
7. Repurposed drugs
Many old drugs, originally developed for other conditions such as diabetes or parasites, or drugs such as beta-blockers, antihistamines and sleeping drugs have been found to have significant benefits against cancer. Metformin, melatonin, propranolol, cimetidine, and mebendazole is just the start of the list. These drugs are all off-patent, are well tolerated and are the subject of increasing research with cancer.
Go to: Old Repurposed drugs in cancer
Anti-cancer drugs
"It is naive to believe that any one drug could defeat a cancer", said American cancer expert Dr. Henry Friedman of Preston Robert Tisch Cancer Center, Dukes, Carolina. His words are increasingly coming true. Many people who develop cancer may find they take 6 or more in succession. It is a complex field. We are updating our list of the top anti-cancer drugs all the time. As you would expect from CANCERactive, they are all written in a patient-friendly, easy to understand way.
Go to: CANCERactive A-Z guide to anti-cancer drugs
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