Average Annual Total Returns — September 30, 2019²

Performance data shown represents past performance and is no guarantee of, and not necessarily indicative of, future results. Total return and value will vary, and you may have a gain or loss when shares are sold. Current performance may be lower or higher than quoted. For most recent month-end performance, visit loomissayles.com. Performance for other share classes will be greater or less than shown based on differences in fees and sales charges. You may not invest directly in an index. Performance for periods less than one year is cumulative, not annualized. Returns reflect changes in share price and reinvestment of dividends and capital gains, if any. The table(s) do not reflect taxes shareholders might owe on any fund distributions or when they redeem their shares.

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Investment Objective

The Fund’s investment objective is long-term capital growth from investments in common stocks or other equity securities.

Market Conditions

Stocks tumbled during the fourth quarter of 2018 over concerns about US Federal Reserve (the Fed) policy tightening, trade wars, and weaker global growth which contributed to a negative turn in investor sentiment. The equity market then staged a remarkable rally during the first nine weeks of 2019 before settling into a trading range for the balance of the 12-month period. Large cap stocks recorded a modest gain for the period, while small cap stocks finished modestly lower.

Lingering investor concerns over the Fed having “overtightened” in 2018, evidence of a softening global economy, and heightened activity related to international trade and tariffs led to increased market volatility throughout the year. Top performers included more defensive investments, including larger capitalization stocks, higher visibility business models, and companies with the healthiest balance sheets.

Interest rates fell fairly dramatically across the maturity spectrum as the result of softer economic data and the Fed moving to an accommodative stance, lowering interest rates twice during the third quarter of 2019.

Small cap growth stocks and value stocks swapped leadership throughout the period with small cap value returns ending just ahead of growth, helped by a stunning value rally in the month of September.

Performance Results

For the 12 months ended September 30, 2019, Institutional Class shares of the Loomis Sayles Small Cap Value Fund returned -4.11% at net asset value. The Fund held up better than its benchmark, the Russell 2000^® Value Index, which returned -8.24%.

Explanation of Fund Performance

The Fund started the fiscal year period positioned fairly conservatively, favoring the upper portion of the market capitalization range and emphasizing companies with highly durable business models. The Fund maintained a fairly significant underweight to the energy sector, which was by far the worst performing area of the small cap market. An overweight to information technology also added to relative performance.

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Stock selection was favorable across most sectors of the Fund, but especially so in the consumer discretionary and health care sectors. Among individual stocks, Mellanox Technologies, Ltd., Aerojet Rocketdyne Holdings, Inc. and Euronet Worldwide, Inc. had the largest positive contributions to performance for the period.

Mellanox Technologies is a leading provider of networking technologies used for high performance and cloud computing. The company has benefited from the explosion of data and proliferation of data centers driving demand for faster networks and interconnects. During the first quarter of 2019, Mellanox agreed to be acquired, providing an additional boost to their share price.

Aerojet Rocketdyne is the leading independent provider of propulsion systems to space, missile defense, and tactical missile customers. It is benefiting from the overall growth of investments in space as well as an increasingly complex geopolitical environment. Profit margins have improved as the company has consolidated its manufacturing footprint.

Euronet facilitates electronic financial transactions on a global basis and manages ATM networks. The stock outperformed as prior regulatory concerns in its electronic funds transfer segment abated and high earnings visibility companies were in favor with investors.

On the negative side, the Fund’s underweight in the “bond proxy” sectors such as real estate and utilities detracted from relative performance, as interest rates declined fairly substantially during the period. Stock selection was also weak within the information technology and financials sectors. During the 12-month period, Conduent, Inc., Avanos Medical, Inc. and Apergy Corporation detracted the most from performance.

Conduent is a leading service company specializing in transaction-intensive services including health savings account administration and toll processing. The company was spun off from Xerox Corporation in 2016 and has made progress reducing its cost structure. However, it has been burdened by legacy technology systems issues and has been unable to add new business as quickly as originally anticipated.

Avanos was spun off from Kimberly-Clark in 2015 and has now transformed itself into a pure-play medical device company. Industry-wide shortages of two pain medications manufactured by Pfizer that are used in the company’s On-Q pain pumps have temporarily constrained top line growth, negatively affecting investor enthusiasm for the stock.

Apergy provides equipment and services in the drilling and production phases of oil and gas wells. Energy stocks were the worst performing sector over the trailing 12 months, and oil services stocks were the weakest segment within energy as rig counts have fallen and drilling companies have cut back on capital expenditures to maintain current wells.

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LOOMIS SAYLES SMALL CAP VALUE FUND

Outlook

We remain committed to identify inefficiencies in the small cap market that result in stock prices and valuations that do not accurately reflect our assessment of the underlying value of the corporate enterprise. We apply this approach consistently over time, regardless of the current market environment.

While many forms of inefficiency may exist in the market, we focus on companies that are misunderstood, underfollowed or in the midst of a “special situation” where we believe we can use our strengths and consistent process. We require fundamentally sound business models, capable management teams and financial stability. Key to our process are distinct, company-specific catalysts on the horizon to sustain, enhance, or highlight the fundamental outlook. These principles are applied consistently over time, regardless of the current market environment. With a margin of safety and a proper time horizon, our goal is to achieve an attractive return for our investors, while managing to an appropriate level of risk.

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Hypothetical Growth of $100,000 Investment in Institutional Class Shares

September 30, 2009 through September 30, 2019³

The portfolio is actively managed and holdings are subject to change. There is no guarantee the Fund continues to invest in the securities referenced. The holdings listed exclude any temporary cash investments.

See notes to chart on page 9.

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Performance data shown represents past performance and is no guarantee of, and not necessarily indicative of, future results. Total return and value will vary, and you may have a gain or loss when shares are sold. Current performance may be lower or higher than quoted. For most recent month-end performance, visit loomissayles.com. Performance for other share classes will be greater or less than shown based on differences in fees and sales charges. You may not invest directly in an index. Performance for periods less than one year is cumulative, not annualized. Returns reflect changes in share price and reinvestment of dividends and capital gains, if any. The table(s) do not reflect taxes shareholders might owe on any fund distributions or when they redeem their shares.

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Investment Objective

The Fund’s investment objective is long-term capital growth from investments in common stocks or other equity securities.

Market Conditions

The 12-month period ending September 30, 2019 was challenging for domestic small cap equities. Mid-cap and large cap equities posted positive returns over the year. After a dramatic selloff in the fourth quarter of 2018, most domestic equity indices bounced back, but the Russell 2500^TM Growth Index (the Index) still finished lower for the period. On a market cap basis, large cap stocks outperformed, as measured by the Russell indices.

The Russell benchmarks showed minimal performance differential between growth and value managers in the small/mid-cap market. Most sectors in the growth benchmark posted negative returns, with energy being a particularly noteworthy underperformer within the Index, losing approximately 48%. The utility sector, however, was an outlier to the upside, posting returns close to 27%.

Performance Results

For the 12 months ended September 30, 2019, Institutional Class shares of the Loomis Sayles Small/Mid Cap Growth Fund returned -3.27% at net asset value. The Fund held up better than its benchmark, the Russell 2500^TM Growth Index, which returned -4.11%.

Explanation of Fund Performance

The Fund’s relative performance was driven by stock selection, with particularly strong contributions from the health care, industrials and financials sectors. Stock selection in the information technology sector detracted from relative performance.

Among individual stocks, the Fund’s top contributors to performance were medical device producer Insulet Corp., electronic fixed income trading platform provider MarketAxess Holdings Inc. and aftermarket aircraft parts supplier Heico Corp. Insulet reported strong results during the year, with healthy international sales after working through inventory issues in the previous quarter. Margins were also strong, and US new patient starts were at an all-time high. The company began distributing into a new channel (pharmacy) which expanded its market reach and ease of access for patients. MarketAxess reported solid results throughout the year, citing improving market conditions for credit trading, and volume trended ahead of prior time periods. Heico benefited from robust demand and a strong pipeline of M&A targets. The market has been favorable for its flight support business, given air-traffic increases and fleet expansion. Rising US defense spending has also benefited its electronic technologies business.

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LOOMIS SAYLES SMALL/MID CAP GROWTH FUND

Conversely, transportation and logistics services company XPO Logistics, cloud-based healthcare management platform provider HealthEquity Inc. and modular space rental solutions specialist WillScot Corp. were the largest detractors to performance for the 12-month time period. The bulk of the impact from these holdings was concentrated in the market selloff of the fourth quarter of 2018. XPO Logistics declined in response to a report from a short-selling investment firm. The logistics company disputed the report’s merit, but given heavy selling pressure across all equities, the stock declined significantly. HealthEquity suffered from concerns around slowing growth and abating catalysts. Despite reporting solid results, expectations were high and investors were disappointed. Concern also grew about the impact of lower interest rates on HealthEquity’s custody business. Finally, WillScot issued stock to warrant holders during poor market conditions, which likely created selling pressure on the stock.

Outlook

As we look forward, we continue to be focused on the underlying business trends of our existing holdings and potential new additions to ensure revenue and earnings growth trends can remain intact. This may prove challenging if earnings estimates continue to see downward pressure.

Markets may be volatile as investors search for clues about the health of the global economy. Central banks appear to be willing to support the global economy, which may reduce some near-term risks. US trade policy remains a source of uncertainty for corporate decision makers and investors. If the US-China trade war is resolved, there could be a rebound in the broader global economy towards the end of the year. Business confidence indicators in the US have shown some signs of weakness, and the inversion of the yield curve further supports the market’s position at the later stages of the cycle. Volatility remains subdued, but macroeconomic and geopolitical events could cause it to return.

While the outlook remains uncertain, we will not attempt to alter our process. As always, we look to deliver to our clients a compelling level of positive risk-adjusted returns that compound over time.

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Hypothetical Growth of $1,000,000 Investment in Institutional Class Shares

June 30, 2015 (inception) through September 30, 2019²

The portfolio is actively managed and holdings are subject to change. There is no guarantee the Fund continues to invest in the securities referenced. The holdings listed exclude any temporary cash investments.

See notes to chart on page 13.

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Performance data shown represents past performance and is no guarantee of, and not necessarily indicative of, future results. Total return and value will vary, and you may have a gain or loss when shares are sold. Current performance may be lower or higher than quoted. For most recent month-end performance, visit loomissayles.com. Performance for other share classes will be greater or less than shown based on differences in fees and sales charges. You may not invest directly in an index. Performance for periods less than one year is cumulative, not annualized. Returns reflect changes in share price and reinvestment of dividends and capital gains, if any. The table(s) do not reflect taxes shareholders might owe on any fund distributions or when they redeem their shares.

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ADDITIONAL INFORMATION

The views expressed in this report reflect those of the portfolio managers as of the dates indicated. The managers’ views are subject to change at any time without notice based on changes in market or other conditions. References to specific securities or industries should not be regarded as investment advice. Because the Funds are actively managed, there is no assurance that they will continue to invest in the securities or industries mentioned.

All investing involves risk, including the risk of loss. There is no assurance that any investment will meet its performance objectives or that losses will be avoided.

Additional Index Information

This document may contain references to third party copyrights, indexes, and trademarks, each of which is the property of its respective owner. Such owner is not affiliated with Natixis Investment Managers or any of its related or affiliated companies (collectively “Natixis Affiliates”) and does not sponsor, endorse or participate in the provision of any Natixis Affiliates services, funds or other financial products.

The index information contained herein is derived from third parties and is provided on an “as is” basis. The user of this information assumes the entire risk of use of this information. Each of the third party entities involved in compiling, computing or creating index information disclaims all warranties (including, without limitation, any warranties of originality, accuracy, completeness, timeliness, non-infringement, merchantability and fitness for a particular purpose) with respect to such information.

Proxy Voting Information

A description of the Funds’ proxy voting policies and procedures is available without charge upon request, by calling Loomis Sayles at 800-633-3330; on the Funds’ website, at www.loomissayles.com, and on the Securities and Exchange Commission’s (“SEC”) website at www.sec.gov. Information about how the Funds voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is available on the Funds’ website and the SEC’s website.

Quarterly Portfolio Schedules

The Funds file a complete schedule of portfolio holdings with the SEC for the first and third quarters of each fiscal year on Form N-PORT. The Funds’ Forms N-PORT are available on the SEC’s website at www.sec.gov.

CFA^® and Chartered Financial Analyst^® are registered trademarks owned by the CFA Institute.

UNDERSTANDING YOUR FUND’S EXPENSES

As a mutual fund shareholder you incur two types of costs: (1) transaction costs and (2) ongoing costs, including management fees, distribution and/or service fees (12b-1 fees), and other fund expenses. Certain exemptions may apply. These costs are described in more detail in the Funds’ prospectus. The following examples are intended to help you

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understand the ongoing costs of investing in the Funds and help you compare these with the ongoing costs of investing in other mutual funds.

The first line in the table of each Fund shows the actual amount of Fund expenses you would have paid on a $1,000 investment in the Fund from April 1, 2019 through September 30, 2019. To estimate the expenses you paid over the period, simply divide your account value by $1,000 (for example $8,600 account value divided by $1,000 = 8.6) and multiply the result by the number in the Expenses Paid During Period column as shown below for your class.

The second line in the table of each Fund provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratios and an assumed rate of return of 5% per year before expenses, which is not the Fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid on your investment for the period. You may use this information to compare the ongoing costs of investing in the Funds to other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of other funds.

Please note that the expenses shown reflect ongoing costs only, and do not include any transaction costs. Therefore, the second line in the table is useful in comparing ongoing costs only, and will not help you determine the relative costs of owning different funds. If transaction costs were included, total costs would be higher.