Mycobacterium tuberculosis bacteria. Image: NIAID, NIH
At a glance:
- A combination of approved cancer drugs may improve tuberculosis treatment.
- In a rabbit model of tuberculosis, the repurposed drugs enhanced delivery of antibacterial medications.
- The drugs also promoted antibacterial responses and improved health outcomes in the animals.
- Next, the combination would need to be tested in patients with tuberculosis.
Researchers have identified a combination of existing cancer drugs that may improve treatment for tuberculosis.
In a study conducted in rabbits and led by Harvard Medical School researchers at Massachusetts General Hospital, the repurposed drugs enhanced delivery of antibacterial medications that target tuberculosis-causing bacteria. Findings published March 27 in PNAS.
Although it is often overlooked in industrialized countries such as the United States, tuberculosis remains one of the deadliest diseases globally, causing millions of deaths every year.
Sometimes, patients die even after being treated, either because tuberculosis bacteria develop resistance to antibacterial drugs or because the ability to deliver medications to infected lung tissue is poor.
To address the latter challenge, researchers repurposed a pair of cancer drugs already approved by the U.S. Food and Drug Administration. The drugs were originally designed to enhance drug delivery to cancer cells by improving the structure and function of blood vessels around tumors, which can be compromised in cancer.
Blood vessel integrity is also an issue in tuberculosis: Often, the disease results in poorly functioning vessels and an overabundant extracellular matrix — the network of proteins and other molecules that surround and give structure to tissues. As a result, blood flow and drug delivery can be reduced in the abnormal lung masses where tuberculosis bacteria reside, allowing the bacteria to evade the body’s immune system.
“Our team is interested in understanding and overcoming physiological barriers to drug delivery” in tuberculosis lung masses, said senior author Rakesh Jain, the Andrew Werk Cook Professor of Radiation Oncology at HMS. “Even the most potent antibacterial drug will fail if it cannot reach the bacteria fueling the disease.”
A multidisciplinary team of engineers, cancer biologists, immunologists, microbiologists, and data analysts used a rabbit model of tuberculosis to test two drugs known as host-directed therapies, or HDTs. One, bevacizumab, acts on blood vessels, and the other, losartan, targets the extracellular matrix.
Previously, Jain and colleagues showed that bevacizumab could improve antibacterial drug delivery to tuberculosis lung masses. Now, they’ve shown that combining bevacizumab with losartan enhances this drug delivery, promotes antibacterial responses, and improves health outcomes. Surprisingly, the HTDs reduced bacteria numbers in lung masses even without antibacterial agents.
To identify the mechanisms involved, the investigators analyzed tuberculosis lung masses and other lung tissue. They found that the HDTs promoted inflammatory responses to tuberculosis bacteria in immune and nonimmune cells.
Also important, bevacizumab and losartan are approved, safe, and affordable, Jain said, so the study lays the groundwork for directly translating the results into the clinic.
A next step, he added, would be “to test these HDTs in patients with tuberculosis for the drugs’ ability to improve outcomes of antibacterial therapy.”
Authorship, funding, disclosures
Additional authors on the paper include Meenal Datta, Laura Via, Véronique Dartois, Danielle Weiner, Matthew Zimmerman, Firat Kaya, April Walker, Joel Fleegle, Isaac Raplee, Colton McNinch, Maksym Zarodniuk, Walid Kamoun, Changli Yue, Ashwin Kumar, Sonu Subudhi, Lei Xu, and Clifton Barry III.
Funding was provided by the Bill & Melinda Gates Foundation (OPP1140482; INV-006974), the National Institutes of Health (F31-HL126449), and the National Institute of Allergy and Infectious Diseases.
Jain received consultant fees from Cur, DynamiCure, Elpis, Merck, SPARC, and SynDevRx. He also owns equity in Accurius, Enlight, and SynDevRx; served on the Board of Trustees of Tekla Healthcare Investors, Tekla Life Sciences Investors, Tekla Healthcare Opportunities Fund, and Tekla World Healthcare Fund; and received research grants from Boehringer Ingelheim and Sanofi. No funding or reagents from these organizations were used in the study.
Adapted from a Mass General news release.
