Clinical Trials

At Prothena, every step we take to heal, cure and prevent disease, we take in collaboration with the patients and their families who generously participate in clinical studies.

Our current clinical programs include birtamimab for AL amyloidosis, prasinezumab for the potential treatment of Parkinson’s disease and PRX004 for the potential treatment of ATTR amyloidosis.

Birtamimab Phase 3
AFFIRM-AL Study for
AL Amyloidosis

Birtamimab is a monoclonal antibody under investigation for the treatment of AL amyloidosis in patients categorized as Mayo Stage IV. Birtamimab is the only investigational therapeutic that has shown a significant survival benefit in Mayo Stage IV patients with AL amyloidosis in a placebo-controlled study, with 74% of birtamimab-treated patients alive at 9 months versus 49% of patients in the control group in the previous Phase 3 VITAL study (hazard ratio (HR)=0.413, p=0.025, over 9 months). The confirmatory AFFIRM-AL study is expected to initiate mid-2021.

Prasinezumab Phase 2 PASADENA Study for Parkinson’s Disease

Prasinezumab is an antibody under investigation as a potentially disease-modifying treatment for Parkinson’s disease, and is the focus of a worldwide collaboration between Prothena and Roche. Results from Part 1 of the PASADENA study in patients with early Parkinson’s disease were reported at the International Congress of Parkinson’s Disease and Movement Disorders in September 2020. Prasinezumab will advance into the Phase 2b PADOVA study in patients with early Parkinson’s disease that is expected to initiate in 2021.

More information is available at, by searching NCT03100149 for the Phase 2 PASADENA Study or NCT04777331 for the Phase 2b PADOVA study

PRX004 Phase 1 Study for
ATTR Amyloidosis

PRX004 is an investigational antibody designed to deplete the pathogenic, non-native forms of the TTR protein (misTTR found in ATTR amyloidosis), without affecting the normal tetrameric form (TTR) of the protein. Positive 9 month results from the Phase 1 long-term extension study were reported in December 2020. PRX004 showed favorable results as demonstrated by slowing of neuropathy progression for all 7 evaluable patients at 9 months, including improvement in neuropathy in 3 of the 7 patients, and improved cardiac systolic function for all 7 patients. In this Phase 1 study, PRX004 was found to be generally safe and well tolerated across all dose levels.

More information on the Phase 1 clinical study of PRX004 in patients with ATTR amyloidosis can be found on, by searching NCT03336580.

Expanded Access Policy

Prothena is committed to developing safe and effective therapies for patients through thoughtful and efficient drug development. We support the need for expanded access programs and our goal is to provide access to study drugs at the appropriate time and in the correct context for patients with life-threatening diseases.

We consider a number of factors when determining whether or not to support expanded access for a given investigational drug:

  • Will it jeopardize the ongoing development work that Prothena is conducting to bring a therapeutic to market as quickly as possible and to as many patients as possible?
  • Is there adequate drug supply for both the clinical development program (current and future trials) and broad expanded access? To be equitable, the company should endeavor to provide study drug to all qualified expanded access patients if it provides study drug to any one patient.
  • Is there enough evidence to assess that the drug will be safe and effective so that it can be provided to a significant number of patients in an environment that is less controlled than a sponsored clinical trial?
  • Can expanded access be offered in accordance with local laws and regulatory requirements?
  • To meet regulatory requirements, will the safety data be adequately provided to Prothena by a local physician outside of a sponsored clinical trial?

Prothena has determined, after assessing these considerations, that expanded access cannot currently be offered for any of our investigational drugs. We periodically re-evaluate this policy and its application to our study drugs.

If and when we provide expanded access for a particular investigational drug, we will review each individual request and respond to the physician who makes the request. During this process, we will need to ensure that:

  • Granting access will not interfere with current clinical trials or regulatory filings.
  • The request is made through a clinician expert in the therapeutic area who has weighed the benefit and risk of providing the investigational drug to the patient.
  • The patient does not qualify for any ongoing or planned clinical trials.
  • The patient has exhausted other therapies that may help him/her.

The above are general requirements, and specific requirements will be generated for a given investigational drug or clinical program if and when Prothena initiates an expanded access program. If you have questions about Prothena’s Expanded Access Policy, please contact us at