New Frontiers
Once seen as a “quirky biological phenomenon” or just cellular trash, exosomes are now the subject of intense medical research for their potential as drug carriers, as treatments in their own right for everything from wound healing and pneumonia to heart attacks and bowel disorders, and as measurable biological markers that could lead to new tests for cancer and other conditions. One exosome-based prostate cancer test, the ExoDx Prostate Test, is already on the market.
The explosion in exosome research — the number of published studies has grown from just a handful in the early 1980s to more than 9000 — spotlights a particular focus on cancer. According to a 2021 paper in Annals of Oncology, clinical trials for exosomes in cancer treatments and tests far out-paces those for diabetes, heart disease, or neurologic conditions. Currently, 52 clinical trials using exosomes in cancer diagnosis or treatment have been completed, are underway, or are looking for participants, according to clinicaltrials.gov.
Dr. Cheng’s approach could also be used to deliver other drugs to the lungs and other organs via inhalation. “We’re testing inhalation for a different type of lung disease, acute lung injury,” Dr. Cheng said. Other potential targets include lung disorders like pulmonary hypertension. Inhaled exosomes could potentially reach the brain via the olfactory bulb or the heart as it receives oxygenated blood from the lungs.
Breathing in Medicine
So far, inhalable cancer treatments are not available outside research studies in the United States or Europe , said Remi Rosiere, PhD, a lecturer at the Université libre de Bruxelles in Brussels, Belgium, and chief scientific officer of InhaTarget Therapeutics, a company developing its own inhaled treatments for severe respiratory diseases. “Oncologists are very interested,” he said. “If you concentrate the drug on the tumor site, you can avoid distribution to the body.”
Early research into inhalable chemotherapy began in the 1960s but was unsuccessful because breathing equipment dispersed toxic cancer drugs into the air or delivered only small amounts to the lungs, he said.
New delivery techniques aim to change that. Dr. Rosiere’s company is starting a human trial of a dry powder inhaler with the chemotherapy drug cisplatin for lung cancer. Also in the pipeline is an immunotherapy treatment for lung cancer inserted in lipid nanoparticles, which are tiny fat particles similar to liposomes.
He said Dr. Cheng’s study shows the advantages of sending in exosomes. “The data are very persuasive,” Dr. Rosier said of the study. “Exosomes have a good safety profile and are able to remain in the lung for quite a long time. This prolongs exposure to the drug for greater effectiveness, without causing toxicities.”
Getting from a mouse study to a human trial will take time. “You need to understand this is very early stage,” Dr. Rosiere added. “There will be many challenges to overcome.”
One is purely practical: If the drug approaches human trials, he said, regulators will ask whether the exosomes can be produced in large quantities to meet the huge demand for new lung cancer treatments. “Lung cancer is the number one fatal cancer in the world,” Dr. Rosiere said.
