Aclaris Therapeutics Added to the NASDAQ Biotechnology Index (NBI)

Aclaris Therapeutics (NASDAQ: ACRS) was added to the Nasdaq Biotechnology Index (NBI), effective at the close of trading on December 19, 2025.

Rhea-AI Summary

Aclaris Therapeutics (NASDAQ: ACRS) was added to the Nasdaq Biotechnology Index (NBI), effective at the close of trading on December 19, 2025. The NBI tracks securities classified as biotechnology or pharmaceutical under the Industry Classification Benchmark and uses a modified capitalization-weighted methodology.

The company met NBI eligibility requirements, including minimum market capitalization, average daily trading volume and public company seasoning; the index is evaluated annually each December.

Positive

• Added to Nasdaq Biotechnology Index effective December 19, 2025
• Met NBI eligibility requirements including market cap, volume and seasoning

Negative

• None.

Argus Dec 22 session

-2.23% close to close 0.4x rel. volume Open Argus

Details

News Market Reaction – ACRS

On Dec 22, the first trading day after this news, ACRS closed 2.23% below the previous close.

Data tracked by StockTitan Argus for the Dec 22 session.

Historical Context

5 past events · Latest: Nov 25

5 events

1. Nov 25

   Conference participation

   24h Move

   -0.7%

   Announcement of CEO participation in Piper Sandler healthcare conference fireside chat.

2. Nov 06

   Earnings and update

   24h Move

   +0.4%

   Q3 2025 financial results and clinical pipeline update including ATI-2138 and bosakitug.

3. Oct 29

   Conference schedule

   24h Move

   -2.1%

   Planned participation in three November healthcare conferences with leadership presentations.

4. Sep 30

   R&D Day announcement

   24h Move

   -1.0%

   Announcement of 2025 R&D Day focusing on immuno-inflammatory pipeline progress.

5. Sep 09

   Clinical data update

   24h Move

   +2.4%

   Late-breaking abstract and oral presentation of ATI-2138 Phase 2a results at EADV Congress.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

Nasdaq Biotechnology Index, Industry Classification Benchmark, capitalization-weighted methodology

3 terms

Nasdaq Biotechnology Index financial

"announced it has been added to the Nasdaq Biotechnology Index (NASDAQ: NBI)"

A stock index that tracks the performance of biotechnology companies listed on the NASDAQ stock exchange, combining many firms into a single measure of the sector’s movement. Think of it as a thermometer or basket that shows whether biotech stocks are generally rising or falling; investors use it to gauge sector health, compare individual holdings against the industry, and as the basis for funds that let you invest in the whole group at once.

Industry Classification Benchmark technical

"classified as either biotechnology or pharmaceutical according to the Industry Classification Benchmark"

A standardized system that groups companies into industries and sectors based on their main business activities, like a library catalog that puts similar books together. It matters to investors because it enables fair comparisons between peers, guides portfolio construction and sector allocation, determines which stocks belong in industry indexes or ETFs, and helps track industry-level risks and performance trends.

capitalization-weighted methodology technical

"The NBI is evaluated annually in December and is calculated under a modified capitalization-weighted methodology"

A capitalization-weighted methodology is a way to build an index or portfolio where each company’s weight equals its total stock-market value, so bigger companies have bigger influence. For investors it matters because performance tracks larger firms more closely, which can make results less sensitive to small companies’ swings — like a playlist where hit songs play more often, shaping the overall listening experience.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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WAYNE, Pa., Dec. 19, 2025 (GLOBE NEWSWIRE) -- Aclaris Therapeutics, Inc. (NASDAQ: ACRS), a clinical-stage biopharmaceutical company focused on developing novel product candidates for immuno-inflammatory diseases, today announced it has been added to the Nasdaq Biotechnology Index (NASDAQ: NBI), effective at the close of trading today, December 19, 2025.

The NBI is designed to track the performance of a set of securities listed on The Nasdaq Stock Market^® that are classified as either biotechnology or pharmaceutical according to the Industry Classification Benchmark. Companies in the NBI must meet eligibility requirements, including minimum market capitalization, average daily trading volume and seasoning as a public company, among other criteria. The NBI is evaluated annually in December and is calculated under a modified capitalization-weighted methodology.

For more information about the Nasdaq Biotechnology Index, please visit this link.

About Aclaris Therapeutics, Inc.

Aclaris Therapeutics, Inc. is a clinical-stage biopharmaceutical company developing a pipeline of novel product candidates to address the needs of patients with immuno-inflammatory diseases who lack satisfactory treatment options. The company has a multi-stage portfolio of product candidates powered by a robust R&D engine. For additional information, please visit www.aclaristx.com and follow Aclaris on X (formerly Twitter) at @AclarisTx and on LinkedIn.

Aclaris Therapeutics Contact:

Will Roberts
Senior Vice President
Corporate Communications and Investor Relations
(484) 329-2125
wroberts@aclaristx.com

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does Aclaris (ACRS) addition to the Nasdaq Biotechnology Index mean for investors?

Aclaris (ACRS) was added to the Nasdaq Biotechnology Index effective Dec 19, 2025, giving the stock index inclusion and potential increased visibility to institutional and passive investors.

When did ACRS officially join the Nasdaq Biotechnology Index (NBI)?

Aclaris (ACRS) was officially added to the NBI at the close of trading on December 19, 2025.

What eligibility criteria did Aclaris meet to join the NBI?

Aclaris met NBI eligibility requirements including minimum market capitalization, average daily trading volume, and public company seasoning.

How often is the Nasdaq Biotechnology Index (NBI) evaluated?

The Nasdaq Biotechnology Index is evaluated annually in December and is calculated under a modified capitalization-weighted methodology.

Will ACRS inclusion in the NBI change the index weighting method?

The index continues to be calculated under a modified capitalization-weighted methodology; Aclaris addition follows that existing methodology.

Where can investors find more information about the Nasdaq Biotechnology Index listing criteria?

For full details on NBI eligibility and methodology, refer to Nasdaq's published index documentation available on the Nasdaq website.