Instead of embarking on one large study it will split the process in two – covering the 2020/2021 and 2021/2022 pollen seasons.
This will allow Allergy to carry out an interim analysis of the data at the halfway stage.
Allergy has opted to split the clinical assessment this way after consulting experts and taking on board feedback from its phase III Birch MATA MPL study.
"The planning for our Grass MATA MPL phase III study is now completed and we look forward to starting this important trial," Allergy chief executive Manuel Llobet said in a statement.
Separately, Allergy said results from the group's successful phase II trial of the grass pollen vaccine, which assessed the dose to be taken into phase III, were recently published in the World Allergy Organisation Journal.
As the name suggests, Allergy Therapeutics, which is headquartered in Worthing, West Sussex and employs around 500 people, develops inoculations against common allergies.
It has five products registered, as well as another five that are available on a named patient basis – this means they can only be prescribed by a doctor.
It has a strong presence in Europe, with established operations in Germany, Italy, Spain, Austria, Switzerland, the Netherlands and the United Kingdom, while in other markets, it often makes its products available through distribution partners.