Taking Drug Delivery into the Inner Ear

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Taking Drug Delivery into the Inner Ear

Inner ear drug delivery

With over 466 million people around the world living with a disabling loss of hearing, and 34 million of these being children, this has scientists, doctors, and researchers all looking for new ways to combat the effects of hearing loss.

When hearing loss occurs after several years of using spoken language, it can be much more difficult to adjust, especially if the loss is profound and not gradual. Those with gradual loss are better able to adapt as they aren’t suddenly rendered with the inability to hear the world around them. They can learn to cope and learn skills over time as they realize they are hearing less and less. For those who wake up one day unable to hear, this transition is much more immediate and imperative.

“Hearing loss has a tremendous effect on self-identity, completeness and confidence to thrive in one’s environment,” explained Peter Steyger, PhD, director of Creighton University’s Translational Hearing Center. The goal of the university is to prevent and treat drug-induced hearing loss.

With a personal connection to this mission, Steyger experienced childhood hearing loss following treatment with aminoglycoside for bacterial meningitis, this is not just a career goal but a personal one as well.

“The loss is more profound when this occurs after infancy, particularly in adults, in those using spoken language. For individuals with progressive hearing loss, this loss continues to exert itself with each progression of hearing loss,” Steyger says.

Researchers are aiming their focus towards preventative treatments as well as restorative methods for dealing with hearing loss. They feel like studies into the inner ear, especially the hair cells located within the cochlea, will lead them in the right direction. Developments into the areas of inner ear drug delivery systems show promise for new treatments for those diagnosed with hearing loss.

“The lack of previous clinical experience in the inner ear field represents a big challenge for companies developing drugs in this space,” noted Hugo Peris, founder and CEO of Spiral Therapeutics, a San Francisco-based clinical-stage pharmaceutical company developing inner ear therapies. “[However], the fact that no drug has been approved to treat any inner ear conditions is also an opportunity.”

Currently, the market has multiple pharmaceutical companies working towards the development of therapies for the inner ear and consequent drug delivery systems to that area. With concentration in the areas of gene therapy, hair cell regeneration, and otoprotection, these developmental projects are still years from hitting the market. Many of which are currently in pre-clinical and clinical trial states at the moment.

“The revolution that we are about to witness in the treatment of hearing loss is extremely exciting. It has been a long time since a specific therapeutic area was so ripe and in so much need for disruption as the inner ear is today,” noted Peris.

One thing these companies are paying special attention to is the drug delivery method for inner ear treatments. They must consider the safety aspects and effectiveness of this delivery as well as the comfort of the patient. It’s just not as easy as taking a pill, drinking a syrup, or getting a shot.

Delivering the Goods

There are three ways to get the needed drugs into the areas of the inner ear that they will do the most good.

  • Intratympanic
  • Intracochlear
  • Systemic

The administration of intratympanic drugs involves getting the mediation through the tympanic membrane (TM), to the middle ear so it can be absorbed through the round window membrane (RWM), then into the cochlea. This is done via a syringe injected into the TM (which is designed to vibrate in response to soundwaves) using solutions or suspensions of drugs as well as injectable gels.

In comparison, the intracochlear administration method is a high-risk procedure requiring that the drugs be transferred directly into the cochlea. This too, uses injection but can also be delivered via reciprocating perfusion system or a mini-pump for osmotic perfusion as well as through a cochlear implant device.

These two methods are the more preferred as it allows professionals to bypass blood-labyrinth barrier (BLB) complications often seen with systemic administration. The BLB is a term that refers to a barrier located between the vascular system and the inner ear fluids either within the membranous labyrinth of the ear or the bone that encloses it.

“Many challenges remain, particularly in understanding the physiology and regulation of the blood-labyrinth barrier that protects the inner ear in the same manner as the blood-brain barrier,” said Steyger. “It is for this reason that many currently efficacious drugs are delivered by one of several local or middle ear delivery mechanisms, to circumvent the blood-labyrinth barrier.”

Due to the low-risk aspect of these methods of drug delivery, professionals are getting behind this application more than others that pose higher risks. Based in clinical settings, this also offers more comfort to patients needing treatment.

“Systemic delivery of therapeutics that target the inner ear is a preferred goal for ease of clinical administration” explained Steyger. “Understanding which systemically administered therapeutics readily enter the inner ear to exert beneficial effects is grossly under-researched at present.”

With new technologies and medical developments popping up around us every day, it won’t be long before hearing loss sees an even bigger shift in the paradigm as to what treatment options are available.

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