Back to the Future: New Drugs from History - PDF

Back to the Future How studying history can help us find new drugs Dr Freya Harrison, School of Life Sciences  Natural products are a vital source of drugs What is a “natural product”? Strict (medicinal chemistry) definition A chemical compound or substance made by a living organism...

Back to the Future How studying history can help us find new drugs Dr Freya Harrison, School of Life Sciences  Natural products are a vital source of drugs What is a “natural product”? Strict (medicinal chemistry) definition A chemical compound or substance made by a living organism That is a secondary metabolite i.e something not strictly essential for survival of the organism Definition usually excludes proteins and refers to “small molecules” Broader definition (good working definition for us) Includes mixtures of NPs (e.g. botanical whole-plant extracts, honey) and may include proteins (defence peptides, enzymes) A global survey of 1,881 drugs approved for clinical use from 1981 – 2019 Synthetic molecules Mimic of natural product 24.6% 22.5% Synthetic molecule inspired by NP 3.2% Vaccines 7.5% Synthetically modified natural product 18.9% Biological macromolecules (mainly peptide/protein) 18.4% Botanical product, defined mixture Natural product, unaltered Data source: 0.8% 3.8% Newman & Cragg J. Nat. Prod. 2020, 83:770  Natural products are a vital source of drugs Antibiotics & antimicrobials are an obvious example of the role of nature in medicine Mainly from NPs made by bacteria and fungi Natural product, unaltered Biological macromolecule Synthetically modified natural product Botanical product  Natural products are a vital source of drugs Plants have generated useful drugs too They make a huge array of secondary metabolites for defence  Today’s lecture Plants as chemical factories Three examples of drugs from plants How studying historical uses of plants as medicine could aid drug discovery A case study of research being led by my research group at Warwick Pacific yew tree Taxus brevifolia Dr Mansukh Wani, 1925-2020, India/USA Dr Monroe Wall, 1916-2002, USA The interest in the Pacific yew tree began in the 1960s when researchers were investigating various plants for their potential medicinal properties. Scientists at the National Cancer Institute (NCI) were screening natural compounds from plants for their ability to combat cancer. In 1962, the compound paclitaxel (also known as Taxol) was isolated from the bark of the Pacific yew tree. Early studies showed that paclitaxel had the ability to inhibit cancer cell division, making it a promising candidate for cancer treatment.  Taxol blocks mitosis by stopping microtubules from depolymerising: Source: Lippincott’s Illustrated Reviews Mainly known for its use against breast, ovarian, cervical cancers Also used for many other cancers too Before surgery: to slow aggressive cancers and reduce chance of metastasis to shrink tumour (may mean breast-conserving surgery is possible instead of mastectomy) After surgery: to reduce risk of cancer returning Generics are available $4.5 Bn $11.2 Bn Global market growth 2021 – 2030 source: Precedence Research Dr Percy Julian, 1899-1975, USA  In the 1940s, Julian and his team were investigating ways to convert stigmasterol (a compound found in soybeans) into Soybean other important Stigmasterol compounds, particularly Glycine max steroid hormones like cortisone and progesterone. While working with stigmasterol, they accidentally discovered that the compound could be converted into testosterone during their experiments. This unexpected result was crucial because testosterone is a precursor to other important hormones, including cortisone. Oestrogen Progesterone Testosterone For menopause, menstrual disorders, contraception, Levonorgestrel for emergency For male hypogonadism, some breast acne, gender-affirming therapy contraception cancers, gender-affirming therapy  Prof. Tu Youyou, born 1930, China < The malaria parasite Plasmodium falciparum and red blood cells Qinghao / Sweet wormwood Ge Hong’s A handbook of prescriptions for Artemisia annua emergencies 317-420 CE  Ethnopharmacology The scientific study of substances used medicinally by different ethnic or cultural groups - especially traditional or “folk” remedies. Could the study of traditional/historical remedies for infection help us restart the stalled discovery pipeline for new drugs to treat bacterial infections? [Insert doom & gloom, impending antibiotic resistance apocalypse here] When we screen environmental microbes for antibiotic compounds, we keep rediscovering molecules we already know about; and screening random libraries of compounds isn’t really helping. Could looking at traditional / historical medicine provide a more focussed approach?  Artemisia annua ↑ Chinese remedy from AD 340 for “intermittent fevers”. Steep wormwood in cold water. ↓ English remedy from 10th Century for “spring disease.” Steep wormwood in Welsh ale. Artemisia absinthium Bald’s Leechbook British Library Royal 12, D xvii © British Library Board An early medieval infection treatment: “Bald’s eyesalve” British Library Royal 12, D xvii © British Library Board, reproduced with permission ?  Steve Diggle & Aled Roberts Nottingham, Cardiff Met In a synthetic mod To work, Bald’s eyesalve has to kill biofilms Bald’s eyesalve is thought to work by disrupting biofilms, which is one of the key mechanisms that contribute to the effectiveness of this ancient remedy. A review article to introduce you to biofilms: Penesyan et al. (2015) Molecules 20:5286  Making biofilms in the lab synthetic collagen wound fluid bacteria Text Choose a bacteria that forms biofilms (e.g., Pseudomonas). Inoculate bacteria in a nutrient medium (like LB broth). Grow in a static environment (e.g., in a well plate) for 24-48 hours. Analyze the biofilm using staining or microscopy  Total Staphylococcus aureus bacteria alive after treatment of biofilms One billion One hundred million Ten million One million One hundred thousand Ten thousand One thousand One hundred Control Eyesalve Onion Garlic Wine Bile 3 batches: A, B, C We need more than one active compound to kill biofilms Explains most bacterial killing in planktonic culture (test tube, liquid) Is not a good drug candidate o Volatile o Irritant The burden of chronic wound biofilm infections Diabetic ulcer infection 5.3M people with diabetes worldwide by 2025 10% will get an infected foot/leg ulcer Venous leg ulcers 2.7M people in Europe Pressure sores 3.7M people in Europe + Burns, SSIs, trauma wounds… Osteomyelitis, sepsis, death Topical/systemic antibiotics + physical treatments Extensive antibiotic resistance 35% increase in cost of care vs. acute wound Annual cost to NHS is £3.2Bn So you have a mixture that kills bacterial biofilms – what next? Defined, chemically characterised mixture? Reproducible manufacturing / effects? Define what dose to use? Is it safe? Does it have any adverse effects? Does it work in vivo? Does it work in an animal model? Does it work in humans?  A pathway for safety testing Cheap and easy… Cell lines …but can over-estimate damage A good middle ground before Ex vivo organ committing to animal models - see 3Rs, below) More realistic Live animal model Can see systemic effects Need special facilities, licences Ethics (Reduce, Refine, Replace: 3Rs) Phase 0 – test a low dose, on healthy Human Phase 0 trial people, to check for harmful effects. (for us, a patch test) If this goes well, you move through phases 1-4 to look in more detail at dosing, side effects and efficacy. Bald’s eyesalve in an ex vivo model of irritation – Bovine Corneal Opacity & Permeability Assay Unstained Fluorescein stain Saline (negative control) Sodium hydroxide (positive control) Eyesalve batch 1 Eyesalve batch 2 Eyesalve batch 3 Bald’s eyesalve in a live animal – wound closure in mice 4.0 No treatment 3.5 Eyesalve 3.0 2.5 Wound size (cm2) 2.0 1.5 1.0 0.5 0 0 5 10 15 Days  Bald’s eyesalve in a human safety trial! We recruited 109 participants, aged 18-77 All healthy with no known allergies or risk factors for a serious reaction – Phase 0/1 They wore a plaster impregnated with 100µl of the eyesalve for 48 hours Then we followed them up to ask if they had any adverse events (AEs: medical occurences that are associated with the patch test, but not necessarily caused by it). AEs can be mild (discomfort, itching) or more serious (e.g. allergic reaction -> anaphylaxis) Two participants were lost to follow-up, and one withdrew due to the garlic smell All mild: redness, itching – AE related to eyesalve: 14 (13.2%) only 1 person reported broken skin AE related to plaster adhesive only: 7 (6.6%) No AE: 85 (80.2%)  Summing up Natural products are important sources of drugs Natural products could help us find new treatments for antibiotic-resistant infections like biofilm infections of chronic wounds Mixtures of natural products can be more effective than single molecules at killing bacterial biofilms The study of traditional/historical medicines could help us find NP mixtures worth exploring in the lab There is a long process of research to move from a mixture in the lab to a formulation that can go into clincial trials! We revised some of the key steps in safety testing There is exciting research happening at Warwick, and you can engage with it J  References Reviews of NP potential in managing infection Salam AM, Quave CL. Opportunities for plant natural products in infection control. Current Opinion in Microbiology. 2018;45:189-94. https://doi.org/10.1016/j.mib.2018.08.004 Quave CL. Wound healing with botanicals: A review and future perspectives. Current Dermatology Reports. 2018;7(4):287-95. 10.1007/s13671-018-0247-4 More info on the the three discovery stores in the first part of the lecture Tu Y. The discovery of artemisinin (qinghaosu) and gifts from Chinese medicine. Nature Medicine. 2011;17(10):1217-20. https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/julian.html https://www.cancer.gov/research/progress/discovery/taxol A review of biofilms and why they are hard to treat Penesyan A, Gillings M, Paulsen I. Antibiotic discovery: combatting bacterial resistance in cells and in biofilm communities. Molecules. 2015;20(4):5286. The Bald’s eyesalve story Harrison F, Roberts AEL, Gabrilska R, Rumbaugh KP, Lee C, Diggle SP. A 1,000-year-old antimicrobial remedy with antistaphylococcal activity. mBio. 2015;6(4):e01129-15. 10.1128/mBio.01129-15 Furner-Pardoe J, Anonye BO, Cain R, Moat J, Ortori CA, Lee C, et al. Anti-biofilm efficacy of a medieval treatment for bacterial infection requires the combination of multiple ingredients. Scientific Reports. 2020;10(1):12687. 10.1038/s41598-020-69273-8 Anonye BO, Nweke V, Furner-Pardoe J, Gabrilska R, Rafiq A, Ukachukwu F, et al. The safety profile of Bald’s eyesalve for the treatment of bacterial infections. Scientific Reports. 2020;10(1):17513. 10.1038/s41598-020-74242-2 Bruce J, Oyedemi B, Parsons N, Harrison F. Phase 1 safety trial of a natural product cocktail with antibacterial activity in human volunteers. Scientific Reports. 2022;12(1):19656. 10.1038/s41598-022-22700-4 A personal view of ethnopharmacology research – in the field and in the lab The Plant Hunter: A Scientist's Quest for Nature's Next Medicines by Cassandra Leah Quave (published by Viking, 2021)