Clinical Trials of D-Methionine: Interview with Kathleen Campbell, PhD
Douglas L. Beck, AuD, spoke with Dr. Campbell about phase 3 clinical trials of D-Methionine, an oral pharmacologic, which may be beneficial to help reduce or prevent noise-induced hearing loss.
Academy: Good morning, Kathy! Great to see you again!
Campbell: Hi, Doug. Thanks, good to be with you, too!
Academy: This is an incredibly important time for you and your research partners! As best I recall, after more than a decade of research, you're just about to enter Phase 3 clinical trials for (the amino acid called) D-Methionine (D-Met)?
Campbell: That's right. The U.S. Food and Drug Administration (FDA) has approved us for a phase 3 clinical trial, as D-Met has demonstrated enormous protective potential with regard to noise-induced hearing loss, drug-induced hearing loss (with regard to platinum-based chemotherapy), as well as aminoglycoside antibiotics (with regard to moderate to severe infections and for treating radiation-induced oral mucositis following radiation treatment for head and neck cancers). D-Met also may be beneficial to help reduce other side effects from chemotherapy and radiation cancer treatments.
Academy: Fantastic. Can you give me a snapshot of Phase 1 and Phase 2?
Campbell: Sure. Phase 1 studies were completed to assure safety and addressed dose escalation safety studies. Phase 2 studies involved clinical trials to reduce cispatin-induced hearing loss in a variety of cancer patients and on radiation induced oral mucositis, which often occurs following radiation treatment for head and neck cancers. The multiple clinical trials combined involved a variety of subject populations.
Academy: But for now, to prevent noise-induced hearing loss and tinnitus, you're working with the United States Department of Defense (DOD)?
Campbell: Exactly. It's been a fantastic collaboration, and we work very well together. They have amazingly dedicated people, disciplined processes, and protocols but with unavoidable noise exposures. The opportunity to help our troops with an oral pharmacologic that may help reduce or prevent noise-induced hearing loss and tinnitus is so interesting and may prove (in time) to be a significant game changer.
Academy: Absolutely. And as a reminder, Kathy, I believe your group discovered and published (17 years ago!) that D-Met protected against hearing loss caused by cisplatin—which was amazing then, and still seems amazing now. So then, this seems like a good time to ask…what is D-Met?
Campbell: D-Methionine is a micronutrient found in common foods such as cheese and yogurt—so it's not alien to the human digestive system. It's a component of high quality fermented protein in the diet and it's been studied for decades in both human and animal nutrition studies as well as our previous clinical trials for chemotherapy (i.e., cisplatin) induced hearing loss and radiation induced oral mucositis. I should note one simply cannot take a whole lot of protein and hope to get the same result, that won't work! It would take over 5 pounds of cheese for a single dose of D-met. Not much fun!
Of note, none of the subjects demonstrated side effects greater in the D-met group than in the placebo group when given the same dosing level proposed for this study (100 mg/kg/day).
Academy: And one of the most impressive findings so far, has been that you should be able to use D-met to rescue noise induced hearing loss. Is that correct?
Campbell: Yes. According to a variety of pre-clinical studies D-met can apparently reverse hearing loss, if started within (up to) 7 hours after noise cessation. We are funded by the Department of Defense for more work to see if we can even wait a few days after noise to first start the D-met and still prevent permanent hearing loss.
Academy: Has anyone else shown D-met protection from hearing loss?
Campbell: I first discovered it here at SIU and patented it but since that time multiple published research studies around the world have confirmed and expanded our findings.
Academy: And I read that D-met is a direct and an indirect antioxidant? And can you explain what that means, please?
Campbell: Well, these terms are difficult to conclusively define without getting into the real chemistry, but here's a way to think about it...Direct antioxidants are the common ones everyone is used to hearing about. These are found in berries, such a cranberries, blueberries, and blackberries, and there are other sources of antioxidants, too, such as beans, artichokes, pecans, walnuts, and hazelnuts, too.
These foods provide direct antioxidants and these same direct antioxidants interact with free radicals to interrupt oxidation, so as to preserve healthy molecules. However, indirect antioxidants are those which are produced by (and within) the body. D-met is both! Of course there are all different types of antioxidants and they can act in different ways.
Academy: Fascinating! Okay, and so D-met seems to be a bit of a "wonder drug," so to speak.
Campbell: Well, we're very hopeful. However, the reason we've gone through all of this work for the last decade or more is to be sure that when we come out with a statement, it is scientifically correct and well documented. As you know, Doug, there are just hundreds and thousands of supplements and vitamins and non-FDA approved claims made for lotions, potions and pills for everything from tinnitus to dizziness to hearing loss and bogus cancer cures and so much more! Many of the ads and some claims made in non-FDA approved "treatments" are just ridiculous, unproven and in some cases unconscionable.
Academy: And so when you've finished Phase 3, the data will be solid, scientifically sound and the claims or outcomes made at that point will be scientifically proven and statistically beyond reproach?
Campbell: That is exactly the goal. But as per protocol, the FDA will require at least one more confirmatory Phase 3 study prior to approval—but that's a very long story, and we'll save it for another day!
Academy: Kathy, this is fascinating work, and I am so impressed with what you're doing, and I'm, very grateful for your time and explanations this morning!
Campbell: My pleasure, Doug. Thanks for your interest in our work!
Kathleen Campbell, PhD, is the professor and director of audiology research in the Division of Otolaryngology, Department of Surgery at SIU School of Medicine andfaculty researcher at Southern Illinois University School of Medicine.
Douglas L. Beck, AuD, Board Certified in Audiology, is the Web content editor for the American Academy of Audiology.