AIT (allergen immunotherapy): a model for the “precision medicine”

The medical science slowly evolved, along centuries, from the Hippocratic “humours”
1] to a more pathophysiology-oriented interpretation of clinical phenomena 2]–4], until the current “omic” sciences. Thus, it seems that a more and more potent magnifying
lens has become available to study and understand diseases. In addition, it is clear
that the clinical science, the mechanistic knowledge and the translational applications
are becoming more and more strictly interconnected.

From the clinical point of view (essentially the therapeutic aspect), a “blockbuster”
approach was applied in clinical practice during the last decades. This attitude was
likely due to a superficial and incomplete knowledge of the underlying mechanisms
of diseases. The advanced insights on the mechanisms and the specific features of
patients’ groups leaded to the definition of phenotypes and endotypes 5], 6]. This “stratification” of groups, in turn, provided a more detailed definition of
diagnosis and treatments, consequently resulting in more appropriate definition of
the eligibility of patients to the different therapeutic tools. The “phenotype driven
therapy” is now a real and urging need, especially when expensive drugs, such as biologicals/biosimilars
have to be prescribed 7], 8]. This aspect is unavoidably linked to sustainability for HealthCare Systems, which
will afford relevant economic burdens. These latter will grow dramatically targeting,
for instance, 30 % of Gross Incoming Product in 2040 in the US 9]. According to those premises we have to face two major reasons for a more selective
approach (phenotyping/endotyping) to the patients who are potentially candidates to
an effective treatment:

medical/scientific aspects

pharmaco-economic aspects.

The “blockbuster approach” (i.e. one size fits all) cannot be currently used with
many of the very expensive treatments available, where the best cost/effective treatment
should be provided. This also implies a greater professional and responsible involvement
of specialists in properly selecting patients. The “precision medicine” can be defined
as a structural model aimed at customizing healthcare at best, with medical decisions,
practices, and/or products tailored on an individual patient. The term of “personalized
medicine” is also used interchangeably.

The major goals of “personalized medicine” are essentially:

to improve the clinical outcomes and their predictability;

to reduce the side effects caused by a possibly inappropriate treatment;

to increase the quality of life;

to encourage patients’ compliance due to a perceived clinical improvement;

to optimise the use of healthcare resources.

Hamburg and Collins 10], described the path to a personalized medicine as summarized in Fig. 1, highlighting the relevant economic investments to pursue this approach: cost/effective
medicine. A pertinent example is the identification, in cystic fibrosis, of one of
the molecular mechanisms that cause the disease: this is present in only 4 % of patients,
but once they are identified, an effective treatment, although expensive, can be given
with expected positive results 11]. Another explanatory example is the specific antagonism to IL-5 in eosinophilic-driven
asthma. Also in this case, it is possible to reasonably identify a priori those candidate
patients who will respond to the targeted biological treatment 12], 13].

Fig. 1. The consequential process underlying personalized medicine

Personalized medicine is still a critical aspect in the most complex, prevalent and
expensive chronic diseases, such as COPD 14] or asthma in general 15], where a targeted approach would heavily affect the management.