Table 2. . Disadvantages and Limitations of Present Immunotherapies.

Humannized mAbs	Peptide therapeutics/T-cell vaccines	Small molecule RTKs
Poor penetration across tissues	In vivo instability, short half-life	Highly toxic, non-specific activity
Ineffective tumor targeting	Low bioavailability, susceptibility to proteases, formulation and manufacturing challenges	Serious side effects
Half life 12 days – requires weekly infusion	Class I MHC restriction limits relevance of individual peptides to certain HLA types
Large quantities of hmAbs resulting intoxicity	Peptides with low affinity for MHC may be poorly immunogenic
Treatment is very expensive	Immune responses transient and/or of low magnitude
Cross-linking leads potential	Large number of peptides required to be useful across a wide range of patients
Immunogenicity	Short peptides may bind directly to MHC which may induce tolerance
Cardiotoxicity, GI perforation
No immunological memory
Treatment not a cure
Resistance to targeted therapies

GI: Gastrointestinal; mAb: Monoclonal antibodies; RTK: Receptor tyrosine kinase.