Microneedle array patches: vaccinations made easy

Dissolvable microneedle array patches (MAPs) consist of tiny, rapidly dissolving needles that can efficiently deliver vaccines into the skin. Their stability over time and easy application gives them great potential to not only simplify the vaccination process during a pandemic, but also in increase vaccination rates in low- and middle-income countries.

In an interview with MEDICA-tradefair.com, Dr. Frank Theobald explains how MAPs can reduce the cold chain requirements of mRNA vaccines and what they have coming up next with the awarded grant from the Bill and Melinda Gates Foundation.  

How exactly do the dissolvable microneedle array patches work?

Dr. Frank Theobald: The fast-dissolving microneedle array patch from LTS consists of 300 microscopically small needles with a length of just 600 µm, which are arranged together over an area of 1 cm². The needles are long enough to penetrate the top layer of skin, but too short to come into contact with pain receptors or blood vessels. They consist of a fast-dissolving polymer in which the active ingredient, in our case the mRNA/LNP (lipid nanoparticle) mixture, is dissolved. After application of the microneedle array patches, the microneedles come into contact with the interstitial fluid and are dissolved within a few minutes. This releases the active ingredient embedded in the microneedles.

What are the advantages of MAPs for mRNA vaccination?

Theobald: By embedding the mRNA/LNPs in polymers, it is possible to reduce the cold chain requirements (for example 5 °C instead of -80 °C). It enables fairer access to vaccinations for people in these [countries with reduced cold chain infrastructure].

MAPs offer the possibility of self-administration, which simplifies administration and avoids the costly establishment of vaccination centers, especially in a pandemic, and relieves the burden on the healthcare system.

As the vaccine is applied intradermally and therefore near the immunocompetent cells in the skin, it is possible to induce a stronger immune response. It is possible to reduce the dose so that more patients can be immunized with the same amount of mRNA.

What challenges have there been so far in the development of MAPs for mRNA vaccine delivery?

Theobald: Two key factors for the development of MAPs are the polymers and the lipid nanoparticles (LNPs) that coat the mRNA. One challenge is the identification of suitable fast-dissolving polymers that can both form mechanically stable microneedles and at the same time have a stabilizing effect on the vaccines.

What are the next steps?

Theobald: As LTS, we want to verify that it is possible to develop a MAP formulation that is stable in terms of its properties (in relation to the active ingredient and the microneedles) for at least 12 months at refrigerator temperatures of 5°C. Ideally, the formulation should also be stable for a certain period of time at 25°C so that the MAPs can be brought to patients without having to maintain a costly cold chain. Ideally, the formulation should also be stable for a certain period of time at 25°C so that the MAPs can be delivered to patients without the time-consuming maintenance of a cold chain.

The focus is also on identifying suitable LNPs that enable optimum stability. In the best-case scenario, a thermostable formulation will be developed that can then be used immediately in a future pandemic.

Apart from vaccine administration, what other medical applications could benefit from MAP technology?

Theobald: In addition to mRNA vaccination, MAP technology is also suitable for vaccination with other vaccines and the application of highly effective biological agents.

Particularly in the treatment of chronic diseases it offers decisive advantages, such as:

• Discrete application,
• Reduction of cold chain requirements, which means that the application can be carried out at any location, thus enabling a normal lifestyle to be maintained,
• Avoidance of infections at the injection site, which can be particularly stressful for patients with chronic diseases.

The technology also offers advantages and interesting possibilities for the application of small molecules, for example through the possibility of forming microimplants for the controlled release of active substances. One example is the development of a long-acting contraceptive MAP. Here too, LTS Lohmann Therapie-Systeme AG has been awarded a grant from the Bill & Melinda Gates Foundation.