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FOLD vs. RIGL: Which Rare Disease Biotech Stock Has Better Upside?
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Key Takeaways
FOLD stands out after agreeing to a $14.50-per-share buyout by BioMarin, expected to be closed in Q2 2026.
FOLD's Galafold drove over 80% of sales in 9M 2025, while Pombiliti plus Opfolda showed strong initial growth.
RIGL's revenues are powered by Tavalisse, with added momentum from Rezlidhia and newly acquired Gavreto.
Amicus Therapeutics (FOLD - Free Report) and Rigel Pharmaceuticals (RIGL - Free Report) appeal to growth-focused investors as they target rare diseases, where small patient populations can still support strong revenue growth.
Amicus is a mid-cap stock compared to Rigel, which is a small biotech. Both companies are engaged in developing and commercializing treatments targeting rare medical conditions where existing therapies are limited.
Amicus’ lead product, Galafold, is the first oral precision medicine approved for treating patients living with Fabry disease, having amenable genetic variants. Rigel’s lead drug is Tavalisse, an oral spleen tyrosine kinase inhibitor, approved for treating adult patients with chronic immune thrombocytopenia (“ITP”) who have had an insufficient response to a previous treatment.
Importantly, for Amicus, a potential takeover from BioMarin Pharmaceutical (BMRN - Free Report) adds another layer of growth upside, as a buyout could accelerate value realization beyond organic sales growth, while Rigel’s upside remains more closely tied to execution on its commercial portfolio and pipeline development.
Let's examine the fundamentals of the two stocks to make a prudent choice.
The Case for FOLD Stock
In December 2025, BioMarin entered into a definitive agreement to acquire all outstanding shares of Amicus for $14.50 per share in cash, totaling $4.8 billion. The deal is expected to be closed in the second quarter of 2026.
Post completion of this acquisition, BioMarin will add Amicus’ marketed products, Galafold and combo drug, Pombiliti (cipaglucosidase alfa) + Opfolda (miglustat). Sales of both these drugs have been growing steadily.
Galafold generates the majority of Amicus’ revenues and has been a key top-line driver for the company in recent quarters. In the first nine months of 2025, Galafold generated sales worth $371.5 million, which increased around 12% on a year-over-year basis. The drug, which has a strong IP portfolio in the United States, providing patent protection through 2038, contributed more than 80% of Amicus’ net product sales during the first nine months of 2025.
Amicus is also making good progress with Pombiliti + Opfolda, a two-component therapy, which is approved for treating adults with late-onset Pompe disease. In the first nine months of 2025, the combo drug generated sales worth $77.5 million, up around 61% on a year-over-year basis. The approval of Pombiliti + Opfolda helped FOLD tap into a market with a significant commercial opportunity.
However, Amicus remains heavily reliant on Galafold for its overall revenue growth, making the company vulnerable to any regulatory setbacks for the drug. Though Pombiliti + Opfolda has been seeing a strong launch, it is yet to generate incremental sales. Also, the company’s lack of a deep pipeline and potential competition from established players with huge resources remains a worry.
The Case for RIGL Stock
Rigel’s first product, Tavalisse, which was launched in the United States in 2018, has been driving the majority of the company’s revenues. The drug generated sales of $113.3 million in the first nine months of 2025, up 54% year over year. The drug remains the key top-line driver for RIGL.
Rigel’s second FDA-approved product Rezlidhia (olutasidenib) is indicated for treating relapsed/refractory acute myeloid leukemia (“AML”) with a susceptible IDH1 mutation. Rezlidhia sales increased 38% year over year during the first nine months of 2025.
Rigel added a third product, Gavreto (pralsetinib), to its portfolio after it acquired commercial rights to the drug from Blueprint Medicines, now part of Sanofi, in 2024. The company started recognizing Gavreto sales from June 2024.
Rigel recently reported preliminary total revenues and net product sales for the fourth quarter of 2025 and provided its financial outlook for 2026. The company also outlined key pipeline goals for 2026. For full-year 2025, Rigel expects to report total revenues of $294.3 million, including net product sales of $232 million and contract revenues of $62.3 million.
RIGL expects preliminary total revenues of $69.8 million for the fourth quarter of 2025, up 21.2% year over year. Preliminary net product sales are expected to be $65.4 million for the fourth quarter of 2025, increasing around 40.6% on a year-over-year basis.
RIGL expects Tavalisse preliminary net product sales of $45.6 million for the fourth quarter of 2025. The company expects Gavreto net product sales of $10.2 million and Rezlidhia net product sales of $9.6 million for the fourth quarter of 2025.
The company projects total revenues of around $275 to $290 million, including net product sales of $255-$265 million.
Rigel has R289 in its pipeline, a novel dual IRAK1 and IRAK4 inhibitor, in an early-stage study for treating patients with lower-risk myelodysplastic syndrome. The company is also exploring Rezlidhia’s (olutasidenib) use beyond relapsed or refractory IDH1-mutated AML into other cancers with IDH1 mutations, such as recurrent glioma.
While Rigel is benefiting from Tavalisse’s success and other commercial efforts, the competitive landscape remains challenging as competition increases in the ITP market.
Last year, the FDA approved Sanofi’s Wayrilz (rilzabrutinib), a novel BTK inhibitor, for the treatment of persistent or chronic ITP in adult patients who have had an insufficient response to a previous treatment. Though Tavalisse and Wayrilz are built on different mechanisms, a successful launch of the latter is likely to pose a significant threat to Tavalisse, given the resources available for a large drugmaker like Sanofi.
How Do Estimates Compare for FOLD & RIGL?
The Zacks Consensus Estimate for Amicus’ 2025 sales and earnings per share (EPS) implies a year-over-year increase of around 19% and 46%, respectively. EPS estimates for both 2025 and 2026 have been trending downward over the past 60 days.
FOLD Estimate Movement
Image Source: Zacks Investment Research
The Zacks Consensus Estimate for Rigel’s 2025 sales and EPS implies a year-over-year increase of around 64% and 564%, respectively. While EPS estimates have increased for 2025, the same for 2026 have been trending downward over the past 60 days.
RIGL Estimate Movement
Image Source: Zacks Investment Research
Price Performance and Valuation of FOLD & RIGL
In the past six months, shares of FOLD have rallied 133.1%, while those of RIGL have surged 87.2%. In comparison, the industry has returned 21.7%, as seen in the chart below.
Image Source: Zacks Investment Research
From a valuation standpoint, Amicus is more expensive than Rigel, going by the price-to-sales (P/S) ratio. FOLD’s shares currently trade at 7.41 times trailing sales value, higher than 2.53 for RIGL.
Image Source: Zacks Investment Research
FOLD vs. RIGL: Which Stock Holds the Edge?
Out of the two stocks discussed above, Amicus, which currently carries a Zacks Rank #3 (Hold), can be backed as the better pick over Rigel, which currently carries a Zacks Rank #5 (Strong Sell).
Despite the limited standalone period before it eventually gets acquired, we remain optimistic about Amicus, supported by the strong sales performance of its marketed products in the first nine months of 2025. Continued growth in Galafold sales should drive its top line, while incremental contributions from Pombiliti + Opfolda are expected to provide additional upside in the days ahead. With FOLD set to be acquired by BioMarin, the stock is best viewed as an event-driven opportunity rather than a long-term growth investment.
By comparison, Rigel’s heavy dependence on Tavalisse for revenues is not a risk-free strategy and underscores the company’s vulnerability to regulatory and competitive risks. Although Tavalisse sales are rising and the company has diversified through Rezlidhia and Gavreto, stiff competition from established players in the target market with huge resources remains a worry.
Overall, FOLD presents a more visible growth story, making it the better pick over RIGL for investors seeking exposure to the rare-disease biotech space right now.
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FOLD vs. RIGL: Which Rare Disease Biotech Stock Has Better Upside?
Key Takeaways
Amicus Therapeutics (FOLD - Free Report) and Rigel Pharmaceuticals (RIGL - Free Report) appeal to growth-focused investors as they target rare diseases, where small patient populations can still support strong revenue growth.
Amicus is a mid-cap stock compared to Rigel, which is a small biotech. Both companies are engaged in developing and commercializing treatments targeting rare medical conditions where existing therapies are limited.
Amicus’ lead product, Galafold, is the first oral precision medicine approved for treating patients living with Fabry disease, having amenable genetic variants. Rigel’s lead drug is Tavalisse, an oral spleen tyrosine kinase inhibitor, approved for treating adult patients with chronic immune thrombocytopenia (“ITP”) who have had an insufficient response to a previous treatment.
Importantly, for Amicus, a potential takeover from BioMarin Pharmaceutical (BMRN - Free Report) adds another layer of growth upside, as a buyout could accelerate value realization beyond organic sales growth, while Rigel’s upside remains more closely tied to execution on its commercial portfolio and pipeline development.
Let's examine the fundamentals of the two stocks to make a prudent choice.
The Case for FOLD Stock
In December 2025, BioMarin entered into a definitive agreement to acquire all outstanding shares of Amicus for $14.50 per share in cash, totaling $4.8 billion. The deal is expected to be closed in the second quarter of 2026.
Post completion of this acquisition, BioMarin will add Amicus’ marketed products, Galafold and combo drug, Pombiliti (cipaglucosidase alfa) + Opfolda (miglustat). Sales of both these drugs have been growing steadily.
Galafold generates the majority of Amicus’ revenues and has been a key top-line driver for the company in recent quarters. In the first nine months of 2025, Galafold generated sales worth $371.5 million, which increased around 12% on a year-over-year basis. The drug, which has a strong IP portfolio in the United States, providing patent protection through 2038, contributed more than 80% of Amicus’ net product sales during the first nine months of 2025.
Amicus is also making good progress with Pombiliti + Opfolda, a two-component therapy, which is approved for treating adults with late-onset Pompe disease. In the first nine months of 2025, the combo drug generated sales worth $77.5 million, up around 61% on a year-over-year basis. The approval of Pombiliti + Opfolda helped FOLD tap into a market with a significant commercial opportunity.
However, Amicus remains heavily reliant on Galafold for its overall revenue growth, making the company vulnerable to any regulatory setbacks for the drug. Though Pombiliti + Opfolda has been seeing a strong launch, it is yet to generate incremental sales. Also, the company’s lack of a deep pipeline and potential competition from established players with huge resources remains a worry.
The Case for RIGL Stock
Rigel’s first product, Tavalisse, which was launched in the United States in 2018, has been driving the majority of the company’s revenues. The drug generated sales of $113.3 million in the first nine months of 2025, up 54% year over year. The drug remains the key top-line driver for RIGL.
Rigel’s second FDA-approved product Rezlidhia (olutasidenib) is indicated for treating relapsed/refractory acute myeloid leukemia (“AML”) with a susceptible IDH1 mutation. Rezlidhia sales increased 38% year over year during the first nine months of 2025.
Rigel added a third product, Gavreto (pralsetinib), to its portfolio after it acquired commercial rights to the drug from Blueprint Medicines, now part of Sanofi, in 2024. The company started recognizing Gavreto sales from June 2024.
Rigel recently reported preliminary total revenues and net product sales for the fourth quarter of 2025 and provided its financial outlook for 2026. The company also outlined key pipeline goals for 2026. For full-year 2025, Rigel expects to report total revenues of $294.3 million, including net product sales of $232 million and contract revenues of $62.3 million.
RIGL expects preliminary total revenues of $69.8 million for the fourth quarter of 2025, up 21.2% year over year. Preliminary net product sales are expected to be $65.4 million for the fourth quarter of 2025, increasing around 40.6% on a year-over-year basis.
RIGL expects Tavalisse preliminary net product sales of $45.6 million for the fourth quarter of 2025. The company expects Gavreto net product sales of $10.2 million and Rezlidhia net product sales of $9.6 million for the fourth quarter of 2025.
The company projects total revenues of around $275 to $290 million, including net product sales of $255-$265 million.
Rigel has R289 in its pipeline, a novel dual IRAK1 and IRAK4 inhibitor, in an early-stage study for treating patients with lower-risk myelodysplastic syndrome. The company is also exploring Rezlidhia’s (olutasidenib) use beyond relapsed or refractory IDH1-mutated AML into other cancers with IDH1 mutations, such as recurrent glioma.
While Rigel is benefiting from Tavalisse’s success and other commercial efforts, the competitive landscape remains challenging as competition increases in the ITP market.
Last year, the FDA approved Sanofi’s Wayrilz (rilzabrutinib), a novel BTK inhibitor, for the treatment of persistent or chronic ITP in adult patients who have had an insufficient response to a previous treatment. Though Tavalisse and Wayrilz are built on different mechanisms, a successful launch of the latter is likely to pose a significant threat to Tavalisse, given the resources available for a large drugmaker like Sanofi.
How Do Estimates Compare for FOLD & RIGL?
The Zacks Consensus Estimate for Amicus’ 2025 sales and earnings per share (EPS) implies a year-over-year increase of around 19% and 46%, respectively. EPS estimates for both 2025 and 2026 have been trending downward over the past 60 days.
FOLD Estimate Movement
Image Source: Zacks Investment Research
The Zacks Consensus Estimate for Rigel’s 2025 sales and EPS implies a year-over-year increase of around 64% and 564%, respectively. While EPS estimates have increased for 2025, the same for 2026 have been trending downward over the past 60 days.
RIGL Estimate Movement
Image Source: Zacks Investment Research
Price Performance and Valuation of FOLD & RIGL
In the past six months, shares of FOLD have rallied 133.1%, while those of RIGL have surged 87.2%. In comparison, the industry has returned 21.7%, as seen in the chart below.
Image Source: Zacks Investment Research
From a valuation standpoint, Amicus is more expensive than Rigel, going by the price-to-sales (P/S) ratio. FOLD’s shares currently trade at 7.41 times trailing sales value, higher than 2.53 for RIGL.
Image Source: Zacks Investment Research
FOLD vs. RIGL: Which Stock Holds the Edge?
Out of the two stocks discussed above, Amicus, which currently carries a Zacks Rank #3 (Hold), can be backed as the better pick over Rigel, which currently carries a Zacks Rank #5 (Strong Sell).
You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.
Despite the limited standalone period before it eventually gets acquired, we remain optimistic about Amicus, supported by the strong sales performance of its marketed products in the first nine months of 2025. Continued growth in Galafold sales should drive its top line, while incremental contributions from Pombiliti + Opfolda are expected to provide additional upside in the days ahead. With FOLD set to be acquired by BioMarin, the stock is best viewed as an event-driven opportunity rather than a long-term growth investment.
By comparison, Rigel’s heavy dependence on Tavalisse for revenues is not a risk-free strategy and underscores the company’s vulnerability to regulatory and competitive risks. Although Tavalisse sales are rising and the company has diversified through Rezlidhia and Gavreto, stiff competition from established players in the target market with huge resources remains a worry.
Overall, FOLD presents a more visible growth story, making it the better pick over RIGL for investors seeking exposure to the rare-disease biotech space right now.