Sifting through countless of stocks in the Biotechnology industry can be tedious, and sometimes two stocks are just too similar to judge which is the better investment. If you’re on the fence about investing in Ultragenyx Pharmaceutical Inc. or Prothena Corporation plc because you’re not sure how they measure up, it’s important to compare them on a few factors before making your decision.

Read on to learn how Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc compare based on key financial metrics to determine which better meets your investment needs.

About Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc

Ultragenyx Pharmaceutical Inc., a biopharmaceutical company, focuses on the identification, acquisition, development, and commercialization of novel products for the treatment of rare and ultra-rare genetic diseases in North America, Latin America, Europe, the Middle East, Africa, and the Asia-Pacific. Its biologic products include Crysvita (burosumab), an antibody targeting fibroblast growth factor 23 for the treatment of X-linked hypophosphatemia, as well as tumor-induced osteomalacia; Mepsevii, an enzyme replacement therapy for the treatment of children and adults with Mucopolysaccharidosis VII; Dojolvi for the treatment of long-chain fatty acid oxidation disorders; and Evkeeza (evinacumab) for the treatment of homozygous familial hypercholesterolemia. The company’s products candidates that are in Phase 3 clinical trials include UX143, a human monoclonal antibody for the treatment of osteogenesis imperfecta; UX111, an AAV9 gene therapy product candidate for the treatment of patients with Sanfilippo syndrome type A, or MPS IIIA, a rare lysosomal storage disease; DTX401, an adeno-associated virus 8 (AAV8) gene therapy clinical candidate for the treatment of patients with glycogen storage disease type Ia; DTX301, an AAV8 gene therapy for the treatment of patients with ornithine transcarbamylase; and GTX-102, an antisense oligonucleotide for the treatment of Angelman syndrome. It also develops UX701, an adeno-associated AAV9 gene therapy which is in Phase 2 clinical trial for the treatment of Wilson liver disease. The company has collaboration and license agreement with Kyowa Kirin Co., Ltd.; Saint Louis University; Baylor Research Institute; REGENXBIO Inc.; GeneTx; Mereo; University of Pennsylvania; Regeneron; and Abeona. Ultragenyx Pharmaceutical Inc. was incorporated in 2010 and is headquartered in Novato, California.

Prothena Corporation plc, a late-stage clinical biotechnology company, focuses on discovery and development of novel therapies to treat diseases caused by protein dysregulation. Its product pipeline includes Prasinezumab, an investigational humanized monoclonal antibody which is in Phase 3 clinical trial for the treatment of parkinson’s disease and other synucleinopathies. The company also develops Coramitug, an investigational antibody, which is in Phase 3 clinical trial for the treatment of transthyretin amyloidosis; BMS-986446, an anti-tau antibody which is in Phase 2 clinical trial to treat Alzheimer’s disease; PRX019, an investigational antibody which is in Phase 1 clinical trial for the treatment of neurodegenerative diseases; and PRX123, a Dual Aß-Tau Vaccine, which is in preclinical trial for treating Alzheimer’s disease. In addition, it develops discovery- and late-preclinical-stage programs include TDP-43 CYTOPE for the treatment of amyotrophic lateral sclerosis; PRX012, a next-generation anti-Aß antibody which is in phase 1 clinical trial to treat Alzheimer’s disease; and PRX012-TfR, a preclinical program for the treatment of Alzheimer’s disease. It has a license, development, and commercialization agreement with F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. to develop and commercialize antibodies that target a-synuclein, including prasinezumab; and master collaboration agreement with Bristol Myers Squibb to develop and commercialize antibodies targeting tau, TDP-43. Prothena Corporation plc was incorporated in 2012 and is based in Dublin, Ireland.

Latest Biotechnology and Ultragenyx Pharmaceutical Inc., Prothena Corporation plc Stock News

As of September 11, 2026, Ultragenyx Pharmaceutical Inc. had a $1.4 billion market capitalization, compared to the Biotechnology median of $269.3 million. Ultragenyx Pharmaceutical Inc.’s stock is NA in 2026, NA in the previous five trading days and down 54.3% in the past year.

Currently, Ultragenyx Pharmaceutical Inc. does not have a price-earnings ratio. Ultragenyx Pharmaceutical Inc.’s trailing 12-month revenue is $717.0 million with a -81.7% net profit margin. Year-over-year quarterly sales growth most recently was 28.1%. Analysts expect adjusted earnings to reach $-3.874 per share for the current fiscal year. Ultragenyx Pharmaceutical Inc. does not currently pay a dividend.

Currently, Prothena Corporation plc does not have a price-earnings ratio. Prothena Corporation plc’s trailing 12-month revenue is $54.5 million with a -80.7% net profit margin. Year-over-year quarterly sales growth most recently was -77.3%. Analysts expect adjusted earnings to reach $0.110 per share for the current fiscal year. Prothena Corporation plc does not currently pay a dividend.

How We Compare Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc Stock Grades

Stock evaluation requires access to huge amounts of data and the knowledge and time to sift through it all, make sense of financial ratios, read income statements and analyze recent stock movements. AAII created A+ Investor, a robust data suite that condenses data research in an actionable and customizable way suitable for investors of all knowledge levels, to help investors streamline and work through such data.

AAII’s proprietary stock grades come with A+ Investor. These offer intuitive A‐F grades for each of five key investing factors: value, growth, momentum, earnings estimate revisions and quality. Here, we’ll take a closer look at Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc’s stock grades to see how they measure up against one another.

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Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc Growth Grades

Company	Ticker	Growth
Ultragenyx Pharmaceutical Inc.	RARE	D
Prothena Corporation plc	PRTA	F

The foundation of growth investing is seeking out stocks of companies exhibiting strong, consistent and prolonged growth that is expected to continue into the future.

In order to compute the growth score and assign it a letter grade, the percentile ranks for each of three components‐consistency of annual sales growth, five-year sales growth rankings adjusted for extreme levels, and consistency of positive annual cash from operations‐must be determined. These three rank figures are added together, and the sum is ranked against the entire stock universe to arrive at a company’s Growth Score to create an equal distribution of grades.

The companies in the bottom 20% of the stock universe receive Growth Grades of F, considered to be very weak, while those in the top 20% receive A grades, which are considered very strong.

Ultragenyx Pharmaceutical Inc. has a Growth Score of 29, which is Weak. Prothena Corporation plc has a Growth Score of 12, which is Very Weak.

The Growth Stock Winner: No Clear Winner

Neither Ultragenyx Pharmaceutical Inc. or Prothena Corporation plc has a high enough Growth Grade to be considered a “winner.” Investors who are considering these companies should do additional due diligence and research to see if either could be a good addition to their portfolios. It’s important to look at a wide range of financial metrics in order to determine if Ultragenyx Pharmaceutical Inc. or Prothena Corporation plc is the better investment when it comes to sustainable growth.

Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc’s Quality Grades

Company	Ticker	Quality
Ultragenyx Pharmaceutical Inc.	RARE	F
Prothena Corporation plc	PRTA	C

Like the Value Grade, AAII’s A+ Investor Quality Grade comes from the percentile rank of key metrics. Specifically, the Quality Score is the percentile rank of the average of the percentile ranks of return on assets (ROA), return on invested capital (ROIC), gross profit relative to assets, buyback yield, change in total liabilities to assets, accruals, Z double prime bankruptcy risk (Z) score and the F-Score.

The score is variable, meaning it can consider all eight measures or, should any of the eight measures not be valid, the remaining measures that are valid. To be assigned a Quality Score, stocks must have a valid (non-null) measure and corresponding ranking for at least four of the eight quality measures.

The Quality Score is used to assess the underlying “quality” of a particular stock. A higher-quality stock possesses traits associated with upside potential and reduced downside risk. Backtesting of the Quality Grade shows that stocks with higher grades, on average, outperformed stocks with lower grades over the period of 1998 through 2019.

Stocks receive better grades (higher scores) for having higher scores for the quality subcomponents and worse grades (lower scores) for lower scores for the subcomponents.

Ultragenyx Pharmaceutical Inc. has a Quality Score of 4, which is Very Weak. Prothena Corporation plc has a Quality Score of 58, which is Average.

The Quality Stock Winner: No Clear Winner

Neither Ultragenyx Pharmaceutical Inc. or Prothena Corporation plc has a high enough Quality Grade to be considered a “winner.” Investors who are considering these companies should do additional due diligence and research to see if either could be a good addition to their portfolios. It’s important to look at a wide range of financial metrics in order to determine if Ultragenyx Pharmaceutical Inc. or Prothena Corporation plc is the better investment when it comes to quality.

Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc’s Estimate Revisions Grades

Company	Ticker	Earnings Estimate
Ultragenyx Pharmaceutical Inc.	RARE	D
Prothena Corporation plc	PRTA	A

Earnings estimate revisions scores consider the magnitude of a company’s earnings surprise in its last two reported fiscal quarters. Often, positive surprises beget further positive surprises‐or at least continued sales growth (the exact opposite is generally true, too).

Estimate revisions offer an indication of what analysts are thinking about the short-term prospects of a firm. Estimate revisions are based on the statistical significance of a firm’s last two quarterly earnings surprises and the percentage change in its consensus estimate for the current fiscal year over the past month and past three months.

Ultragenyx Pharmaceutical Inc. has a Earnings Estimate Score of 36, which is Negative. Prothena Corporation plc has a Earnings Estimate Score of 98, which is Very Positive.

The Earnings Estimate Revisions Grade Winner: Prothena Corporation plc

As you can clearly see from the Earnings Estimate Revisions Grade breakdown above, Prothena Corporation plc has a better Earnings Estimate Revisions Grade than Ultragenyx Pharmaceutical Inc.. For those who are specifically looking for companies with better short-term prospects when compared to other companies in the same industry, Prothena Corporation plc could be a good stock to invest in. However, it’s important to analyze multiple factors based on a wide range of metrics before deciding whether to buy.

Other Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc Grades

In addition to Growth, Quality and Estimate Revisions, A+ Investor also provides grades for Value and Momentum.

Momentum grades help uncover stocks experiencing anomalously high rates of return; research finds that stocks with high relative levels of momentum tend to outperform, whereas those with low levels of momentum tend to continue underperforming.

Successful stock investing involves buying low and selling high, so stock valuation is an important consideration for stock selection. Buying stocks that are going to go up typically means buying stocks that are undervalued in the first place, although momentum investors may argue that point.

These 2 key factors, when combined with the above, provide a holistic view into a particular stock. Further, by joining A+ Investor you can see whether Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc pass any of our 60+ stock screens that have outperformed the market since their creation.

So, Which Is the Better Investment, Ultragenyx Pharmaceutical Inc. or Prothena Corporation plc Stock?

Overall, Ultragenyx Pharmaceutical Inc. stock has a Growth Score of 29, Estimate Revisions Score of 36 and Quality Score of 4.

Prothena Corporation plc stock has a Growth Score of 12, Estimate Revisions Score of 98 and Quality Score of 58.

Comparing Ultragenyx Pharmaceutical Inc. and Prothena Corporation plc’s grades, scores and metrics can act as a solid basis to determine whether they may be a good investment or not. You’ll also want to look at your portfolio’s asset allocation as well as your risk tolerance and financial goals to see if either of these stocks would make a good fit for you. AAII can help you figure out which investments align with your individual needs and preferences.

Investors are encouraged to do their own due diligence and research. In this way, individuals can effectively become managers of their own assets‐without having to rely on others for financial independence. You can count on AAII for timeless articles on financial planning and stock-picking, unbiased research and actionable analysis.

A+ Investor adds to our qualitative teaching with a powerful data suite to help you whittle down investment choices to find stocks, exchange-traded funds (ETFs) or mutual funds that meet your needs.

AAII Disclaimer

We make no representations or warranties that any investor will, or is likely to, achieve profits similar to those shown, because past, hypothetical or simulated performance is not necessarily indicative of future results. Before making an investment decision, you should consider your circumstances and whether the information on our content is applicable to your situation. This information was prepared in good faith, and we accept no liability for any errors or omissions. The full disclaimer can be read here.