Researchers are developing an injection that creates a contraceptive implant in the body using an approach that could herald a new way of delivering drugs over long periods of time.
Current contraceptive implants last for years, meaning women do not have to take a pill every day, but the devices must be fitted by a trained professional via a small surgical procedure. Contraceptive injections are already available but they have limitations, including that they last for only three months.
Now scientists say they have completed proof-of-concept experiments for a new type of long-lasting implant that self-assembles in the body.
While not yet tested in humans, the researchers behind the work say the approach could bring benefits beyond the field of birth control, offering a simple way to administer long-acting drug delivery systems without the need for invasive procedures – an appealing prospect for parts of the world with poor medical infrastructure.
“It’s suitable for any poorly soluble hydrophobic drug, especially where long-acting delivery is needed. This includes treatments for HIV, TB, schizophrenia, chronic pain, or metabolic disease,” said Dr Giovanni Traverso, a co-author of the study from the Massachusetts Institute of Technology and a gastroenterologist at Brigham and Women’s hospital in the US.
The approach involves injecting micro-crystals of a synthetic version of the hormone progesterone contained in a solvent that does not mix well with water.
Once in the body, the solvent exchanges with bodily fluid. However, the micro-crystals prefer to clump together than interact with this water-rich environment. This, together with the formation of further crystals as the solvents exchange, results in the development of a solid implant, capable of releasing the drug slowly over time.
The team, whose study was published in the journal Nature Chemical Engineering, tested the approach in rats, allowing them to refine the choice of solvent in the injection. The drug release in rats was sustained for at least 97 days, although Traverso said there was potential for longer durations depending on formulation adjustments.
“The dosing and volumes of drug are compatible with multi-year dosing,” he said, adding that the formation of a solid implant means it can be removed if required, while the approach is also compatible with the use of small needles.
However, the research is still in its early stages, with the efficacy of the approach yet to be tested. “It lays the groundwork for future human studies which we hope will start in the next three to five years,” Traverso said.
Dr Janet Barter, the president of the Faculty of Sexual and Reproductive Healthcare, said the approach could be an exciting advancement.
