Theophylline Nasal Spray for PD-Related Hyposmia and Anosmia

Inclusion Criteria: * Able to provide written informed consent. * 19-80 years of age. * Subjective or clinically diagnosed hyposmia/anosmia \> 6 months with onset related to Parkinson's Disease. Note: participants may be rescreened at a later time if duration of hyposmia is determined to be \< 6 months. * Hyposmia defined as ≤5 on the NRS-11 Smell-PRO smell scale (scale of 0-10; 10 indicating normal sense of smell, 0 indicating no sense of smell). * Hoehn and Yahr scale is \<3. * Montreal Cognitive Assessment (MOCA) score \>24. * Endoscopy of the nasal cavity showing no structural or pathologic issues leading to hyposmia (nasal polyps, sinusitis, infection, etc.) that in the opinion of the Investigator, believes would hinder the delivery of study drug to the olfactory region of the nasal cavity. * Willing and able to self-administer the study drug, follow the study drug administration instructions, comply with study procedures, and participate in the scheduled study visits specified in this protocol. * Score Sniffin Sticks Olfactory Test Threshold, Discrimination and Identification (TDI) at baseline and EOS. Exclusion Criteria: * Hyposmia due to other causes (non-Parkinson's Disease related): * History of traumatic brain injury, viral related smell loss or any other condition in which hyposmia is not expected to improve in the opinion of the Investigator, such as history of congenital or idiopathic hyposmia or a surgical procedure that led to hyposmia. * History of sy…