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A drug repurposing study of tamoxifen for a deadly form of fungal meningitis suggests it has no benefits in clearing the infection more quickly.

Hopes that tamoxifen could improve survival for a deadly form of fungal meningitis have been dashed by clinical trial results published in eLife.

The study finds that adding tamoxifen to standard antifungal treatment was no better at speeding up the clearance of fungal infection from the spinal fluid of people with meningitis. More patients who received tamoxifen had evidence of conduction disturbances in their hearts, although there was no difference in the rates of severe side effects between study groups. 

Cryptococcal meningitis is a leading cause of death in people with HIV, but also affects those without HIV, regardless of whether they are immunocompromised. Most infections are caused by a fungus called Cryptococcus neoformans (C. neoformans) and occur in low-income tropical settings. The gold-standard treatment is a combination of three drugs: flucytosine and amphotericin B initially, followed by fluconazole. Yet, even on this gold-standard therapy, a third of patients die within 10 weeks of being diagnosed. Moreover, the drug flucytosine is severely restricted by availability and cost, meaning it is rarely used where the disease burden is highest.

“Tamoxifen has shown antifungal activity against various yeasts in the lab; we subsequently showed that it acts synergistically with amphotericin against two-thirds of clinical Cryptococcus isolates from our archive. As a well-understood, off-patent, cheap and widely available medicine, it was a promising candidate for treating cryptococcal meningitis,” explains co-first author Nguyen Thi Thuy Ngan, Clinician at the Department of Tropical Medicine, Cho Ray Hospital, and the Oxford University Clinical Research Unit (OUCRU), Ho Chi Minh City, Vietnam. 

“We designed a randomised trial to determine whether using these drugs in combination could improve the speed of clearance of Cryptococcus from patients with meningitis with and without HIV,” adds co-first author Nhat Thanh Hoang Le, Biostatistician at OUCRU.

The trial involved 50 patients – 40 had HIV and 10 did not. Of the patients, 24 were assigned to receive a standard anti-fungal treatment of amphotericin B and fluconazole plus tamoxifen, and 26 received the standard anti-fungal treatment only. The team measured the Early Fungicidal Activity (EFA) for both groups – that is, how quickly there was a decline in the amount of C. neoformans in a patient’s spinal fluid in the two weeks following treatment.

Based on their prior experiments, the team had hoped to see better EFA for patients who had tamoxifen added to the antifungal treatment. However, there was no detectable difference in EFA.

The only difference seen between the two treatment groups was the increased heart toxicity in the tamoxifen group. Studies in the lab had shown that a tamoxifen dose 5–10 times higher than that used routinely in breast cancer would be needed to have an antifungal effect. But a high dose of tamoxifen is known to cause an effect on the heart called QT prolongation – an  abnormality that can cause cardiac arrest. There was one sudden death in the tamoxifen group in this study, although this occurred after the period of tamoxifen administration and it was not associated with an abnormal heart rhythm.

“Despite its apparent anti-cryptococcal effect and synergy with other drugs, tamoxifen does not increase the rate of clearance of yeast from spinal fluid in people with meningitis and is unlikely to result in clinical benefit,” concludes senior author Jeremy Day, Head of the CNS and HIV Infections Research Group at OUCRU, and Professor of Infectious Diseases at the Centre for Tropical Medicine and Global Health, Oxford University, UK. 

“Our results show the importance of small-scale trials such as this for rapidly evaluating repurposable drugs and preventing the time and cost of a larger clinical study that is likely to fail. However, sadly this does mean that we urgently still need new, specific anti-cryptococcal drugs to be developed, and we also need to ensure that existing, available treatments are made accessible and affordable.”

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For more information, contact: Communications@oucru.org

Using cutting-edge genomic sequencing techniques, researchers at the University of Oxford have identified almost all the genomic variation that gives people resistance to 13 of the most common tuberculosis (TB) drug treatments.

The Comprehensive Resistance Prediction for Tuberculosis International Consortium (CRyPTIC) research project has collected the largest ever global dataset of clinical M. tuberculosis samples from across the world consisting of 15,211 samples from 27 countries on five continents.

Using two key advances: a new quantitative test for drug resistance and a new approach which identifies all the genetic changes in a sample of drug-resistant TB bacteria the researchers have generated a unique dataset which the team has used to quantify how changes in the genetic code of M. tuberculosis reduce how well different drugs kill these bacteria that cause TB. These innovations, combined with ongoing work in the field, promise to profoundly improve how patients with TB are treated in the future.

Tuberculosis kills more people each year than any other bacterium, virus, or parasite, except for SARS-CoV-2. Although it is treatable, drug resistance has emerged as a major problem over the past 3 decades. Testing for mutations in the M. tuberculosis genome to determine which drugs will give a patient the best chance of cure is the most realistic way of getting drug resistance testing to every patient who needs it.

“This has been a massive international effort over five years, and will translate into benefits for patients and the wider community as these data are implemented to diagnose and manage drug-resistant TB effectively, and thereby reduce its onward transmission,” said Dr Timothy Walker, Wellcome Fellow at the Oxford University Clinical Research Unit (OUCRU) and Associate Professor at the University of Oxford.

In a series of nine new preprint manuscripts, each documenting a different aspect of how the CRyPTIC project has advanced the field, the researchers reveal:

• How the new drug resistance tests should be interpreted [1] and how a massive citizen science project helped solve this problem [2]
• How a new approach to detecting and describing genetic changes in the whole TB genome sequence improved the way genetic changes driving drug resistance can be detected [3]
• How these data were used to scan the TB genome sequence for changes not previously known to cause drug resistance [4]
• How individual mutations, and combinations of mutations, can be related not just to blunt measures of ‘resistance’ or ‘susceptibility’, but also to even minor changes in the way a drug kills M. tuberculosis, thereby reducing the effectiveness of treatment [5] with special attention being paid to two novel compounds being used to treat tuberculosis [6].
• How artificial intelligence can predict drug resistance from signatures in the DNA sequence [7]
• How these data [8] contributed to the first list of drug resistance mutations in the TB genome to be endorsed for global use by the World Health Organization [9]

These results aim to help improve control of tuberculosis and facilitate the World Health Organisation’s end TB strategy through better, faster and more targeted treatment of drug-resistant tuberculosis via genetic resistance prediction, paving the way towards universal drug susceptibility testing (DST).

“Ongoing international collaborations like this are essential if we are to continue to drive forwards our understanding of infectious diseases and how to treat them. As we know from recent experience with COVID-19, such advances benefit everyone,” Dr Walker highlighted.

The data, which are now freely available, can be used by the wider scientific community to improve our understanding of drug resistance in TB and how to best treat this important disease.

This project is funded by MRC Newton Fund, Wellcome, and Bill & Melinda Gates Foundation. Dr Walker’s team is based in Ho Chi Minh City, Viet Nam, with the Oxford University Clinical Research Unit (OUCRU), one of five Wellcome’s Asia Africa Programmes.

For further information, or to request an interview, please contact the Communications team at Oxford University Clinical Research Unit (OUCRU) at communications@oucru.org

Manuscripts:

1. Epidemiological cutoff values for a 96-well broth microdilution plate for high-throughput research antibiotic susceptibility testing of M. tuberculosis. The CRyPTIC Consortium (2021) medRxiv preprint. https://doi.org/10.1101/2021.02.24.21252386
2. BashTheBug: a crowd of volunteers reproducibly and accurately measure the minimum inhibitory concentrations of 13 antitubercular drugs from photographs of 96-well broth microdilution plates. Fowler PW et al. (2021) biorXiv preprint. https://doi.org/10.1101/2021.07.20.453060
3. Minos: variant adjudication and joint genotyping of cohorts of bacterial genomes. Hunt M et al. (2021). bioRxiv preprint. https://doi.org/10.1101/2021.09.15.460475
4. Genome-wide association studies of global Mycobacterium tuberculosis resistance to thirteen antimicrobials in 10,228 genomes. The CRyPTIC Consortium (2021). bioRxiv preprint. https://doi.org/10.1101/2021.09.14.460272
5. Quantitative measurement of antibiotic resistance in M. tuberculosis reveals genetic determinants of resistance and susceptibility in a target gene approach. The CRyPTIC Consortium (2021). bioRxiv preprint. https://doi.org/10.1101/2021.09.14.460353
6. Deciphering Bedaquiline and Clofazimine Resistance in Tuberculosis: An Evolutionary Medicine Approach. Sonnenkalb L et al. (2021) biorXiv preprint. https://doi.org/10.1101/2021.03.19.436148
7. A generalisable approach to drug susceptibility prediction for M. tuberculosis using machine learning and whole-genome sequencing.  The CRyPTIC Consortium (2021). bioRxiv preprint. https://doi.org/10.1101/2021.09.14.458035
8. A data compendium of Mycobacterium tuberculosis antibiotic resistance. The CRyPTIC Consortium (2021) bioRxiv preprint. https://doi.org/10.1101/2021.09.14.460274
9. The 2021 WHO catalogue of M. tuberculosis complex mutations associated with drug resistance: A new global standard for molecular diagnostics. Walker et al. (2021) Lancet preprint. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3923444 http://www.crypticproject.org/wp-content/uploads/2021/09/CRyPTIC9-WHO-preprint.pdf

Note that since these manuscripts are preprints, they have not yet undergone academic peer-review.

The malaria parasite Plasmodium vivax (P. vivax) causes frequent, chronic infections that represent a major unrecognized burden on global health, according to a review by Kevin Baird of the Eijkman-Oxford Clinical Research Unit in Indonesia and Katherine Battle of the Institute for Disease Modeling in the United States publishing October 7^th in the open access journal PLOS Medicine.

In this review, Baird and Battle summarize evidence indicating that the global burden of malaria estimated from reported cases of acute attacks likely miss the widespread but more subtle harm done by chronic infection of P. vivax. Futhermore, P. vivax often affects impoverished communities where people face multiple health challenges. There are five Plasmodium species that cause malaria, but the vast majority of reported cases are due to Plasmodium falciparum, with about 193.5 million cases annually. P. vivax is the second most commonly reported cause, with about 14.3 million cases annually. A recent study found that while P. falciparum is more likely to cause death within two weeks of diagnosis, patients with P. vivax were more than twice as likely to die over the long term. Chronic infections in people who are repeatedly exposed to P. vivax cause damage to the kidneys, brain, and circulatory system.

An improved understanding of the biology of P. vivax has recently revealed multiple factors that contribute to its toll on global health. The parasite can exist in the body at low levels that cause no symptoms, making it difficult to diagnose, but can still spread. Sub-Saharan Africa was once thought to be practically immune to P. vivax infection because most of the population lack the Duffy antigen, a molecule on the surface of red blood cells the parasite uses to invade. However, a recent study finds that P. vivax transmission is still widespread in this region. Additionally, there are two common genetic variations carried by part of the population that interfere with successful treatment of P. vivax malaria.

All these factors complicate efforts to estimate the full extent of P. vivax infections and control its spread. Baird and Battle conclude that the traditional approaches developed to combat P. falciparum in Africa are inadequate for P. vivax. Eliminating P. vivax will require different diagnostics, therapies and vector control strategies, and better data that reveal the true scope of the burden.

Baird adds, “Blood smears from patients suffering acute vivax malaria do not suffice to measure global burdens of this infection. The parasite finds refuge in deeper organs where the harm done is more subtle but nonetheless substantial.”

Prof. Kevin Baird appeared on Outbreak News TV to discuss Plasmodium vivax. 

This paper is freely available in PLOS Medicine

Contact: Prof. Kevin Baird

• Email: kevin.baird@ndm.ox.ac.uk
• Mobile phone: +62-8131-647-4625

Citation: Battle KE, Baird JK (2021) The global burden of Plasmodium vivax malaria is obscure and insidious. PLoS Med 18(10): e1003799. https://doi.org/10.1371/journal.pmed.1003799 

It has come to our attention that a recent post from the Children’s Health Defense on 23^rd August 2021 shared the false claim that our paper demonstrated “vaccinated individuals carry 251 times the load of COVID-19 viruses in their nostrils compared to the unvaccinated”.

SARS-CoV-2 Delta variant infection is associated with high viral loads, which has been demonstrated in recent studies from various countries (including China (ref#1), Singapore (ref#2), the UK (ref#3), and the US (ref#4&5)). The study from China showed that viral loads in people infected with the Delta variant were 1000 times higher than those infected with the 19A/19B strains detected in China in early 2020. Additionally, the studies from the US, the UK and Singapore demonstrated that vaccinated and unvaccinated individuals infected with SARS-CoV-2 Delta variant carried the same amounts of the virus in their respiratory tracts, with a faster viral clearance rate observed in vaccinated people (according to the study from Singapore).

In our study (https://ssrn.com/abstract=3897733), we compared viral loads (inferred from PCR Ct values) from cases infected with the original SARS-CoV-2 strains detected in Vietnam between March and April 2020 (herein referred to original strains) with those from fully vaccinated healthcare workers infected with SARS-CoV-2 Delta variant.

Similar to data from the aforementioned studies, we showed that Delta variant infections in fully vaccinated healthcare workers were associated with high viral loads, and indeed were 250 times higher than those in people infected with the original strains. The differences in viral load were driven by the ability of the Delta variant to cause higher viral loads; they had nothing to do with the vaccination status of the infected individual. Thus the claim that vaccinated individuals carry 251 times the loads of SARS-CoV-2 in their respiratory tract compared to the unvaccinated people is a misrepresentation of the data.

There is overwhelming evidence for the effectiveness of vaccines in preventing severe disease and death from COVID-19. Our study provides no evidence to the contrary. We strongly endorse vaccination as a critical tool against COVID-19 and the terrible consequences of the pandemic.

Nguyen Van Vinh Chau, MD, PhD – Director of Hospital for Tropical Diseases, Ho Chi Minh City

Professor Guy Thwaites, MD, PhD  – Director of OUCRU

Le Van Tan, PhD – Head of Emerging Infections Group, OUCRU

References

1. Viral infection and transmission in a large, well-traced outbreak caused by the SARS-CoV-2 Delta variant, https://www.medrxiv.org/content/10.1101/2021.07.07.21260122v2.full.pdf+html

2. Virological and serological kinetics of SARS-CoV-2 Delta variant vaccine-breakthrough infections: a multi-center cohort study, https://www.medrxiv.org/content/10.1101/2021.07.28.21261295v1

3. Impact of Delta on viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK, https://www.medrxiv.org/content/10.1101/2021.08.18.21262237v1

4. Shedding of Infectious SARS-CoV-2 Despite Vaccination, https://www.medrxiv.org/content/10.1101/2021.07.31.21261387v4.full.pdf+html

5. Outbreak of SARS-CoV-2 Infections, Including COVID-19 Vaccine Breakthrough Infections, Associated with Large Public Gatherings — Barnstable County, Massachusetts, July 202, https://www.cdc.gov/mmwr/volumes/70/wr/mm7031e2.htm

To improve the diagnosis of all forms of TB at any age, the OUCRU TB team is participating in the international ENDxTB project, funded 2020 – 2025 by NIH. We provide clinical experience and laboratory skills to evaluate field-ready diagnostic tests and platforms for TB in Vietnam, in collaboration with Pham Ngoc Thach Hospital and District TB Units in Ho Chi Minh City.

See more: https://www.endxtb.com/