First Trust Developed Markets ex-US Small Cap AlphaDEX Fund (FDTS) Exchange: NASDAQ

The Fund will normally invest at least 90% of its net assets (including investment borrowings) in the common stocks, depositary receipts, real estate investment trusts ("REITs") and preferred shares that comprise the Index. The Fund, using an indexing investment approach, attempts to replicate, before fees and expenses, the performance of the Index. The Fund's investment advisor seeks a correlation of 0.95 or better (before fees and expenses) between the Fund's performance and the performance of the Index; a figure of 1.00 would represent perfect correlation. The Index is owned and is developed, maintained and sponsored by Nasdaq, Inc. (the "Index Provider"). The Index Provider may, from time to time, exercise reasonable discretion as it deems appropriate in order to ensure Index integrity.The Index is composed of securities issued by small cap companies operating in developed market countries excluding the United States, as classified by the Index Provider. The Index Provider classifies a country as "developed" based on a number of criteria, including national income per capita, national market capitalization and national trading volume. Companies are classified as operating in a country primarily by their country of incorporation, domicile and primary exchange listing. The Index may be composed of securities denominated in non-U.S. currencies. The Index is designed to select stocks from the NASDAQ Developed Markets ex-US Index (the "Base Index") that may generate positive alpha, or risk-adjusted returns, relative to traditional indices through the use of the AlphaDEX® selection methodology. Alpha is an indication of how much an investment outperforms or underperforms on a risk-adjusted basis relative to its benchmark. The Base Index is a comprehensive, rules-based index designed to measure stock market performance of companies in developed market countries excluding the United States, as determined by the Index Provider.Security selection for the Index will be conducted in the following manner:1.The selection universe for the Index begins with all stocks in the Base Index.2.The Index Provider then removes any stocks which do not trade on an eligible exchange; duplicate (multiple share classes) stocks; stocks which do not meet the Index Provider's liquidity screens; and stocks with a market capitalization greater than the mid cap breakpoint (50th percentile) and less than the small cap breakpoint (90th percentile) as calculated by Nasdaq. As of March 31, 2020, the mid cap breakpoint was $2.195 billion and the small cap breakpoint was $219.563 million.3.For South Korean stocks currently at their foreign ownership limit, the direct listed security is replaced in the universe with its depositary receipt if available (subject to above liquidity requirements). If none is available, the stock is excluded.4.The remaining stocks in the universe are then ranked on both growth and value factors. Each stock receives the best style rank from this step as its selection score.5.The top 400 stocks based on the selection score determined in step 4 comprise the "selected stocks." The selected stocks are then split into quintiles based on their selection score, with higher scoring quintiles receiving a greater weight in the Index.6.The Index is subject to sector/country weighting constraints which are set at 15% above the sector/country percentages of the Base Index. A stock will be moved to a lower-weighted quintile when its weight, added to the weight assigned to all higher ranking stocks in its sector/country, is greater than the sector/country weighting constraint. Stocks that fail the sector/country weighting constraints at the lowest quintile will be removed from the Index.The Index is rebalanced and reconstituted semi-annually and the Fund will make corresponding changes to its portfolio shortly after the Index changes are made public. The Index's semi-annual rebalance and reconstitution schedule may cause the Fund to experience a higher rate of portfolio turnover. The Fund will be concentrated in an industry or a group of industries to the extent that the Index is so concentrated. As of March 31, 2020, the Index was composed of 395 securities and the Fund had significant investments in industrials companies, Japanese issuers, Asian issuers and European issuers, although this may change from time to time. To the extent the Fund invests a significant portion of its assets in a given jurisdiction or investment sector, the Fund may be exposed to the risks associated with that jurisdiction or investment sector.