TIMELY INFORMATION INSIDE

Global Dynamic Income Fund (CHW)

SEMIANNUAL REPORT APRIL 30, 2020

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TABLE OF CONTENTS

CALAMOS CLOSED-END FUNDS

Innovative Solutions for
the Search for Income

About Calamos Investments:

•An innovator in dynamically allocated closed-end funds since 2002

•Funds offer competitive distributions through our multi-asset class approach and strategies that have been less dependent on interest rates

•Total return and enhanced fixed income funds can meet a range of investor needs

•Distribution policies seek to provide steady monthly income

•Currently managing more than $6.8 billion in seven closed-end funds*

*As of 4/30/2020.

John P. calamos, sr.

Founder, Chairman
and Global Chief
Investment Officer

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   1

Dear Fellow Shareholder,

Welcome to your semiannual report for the six-month period ended April 30, 2020. In this report, you will find commentary from the Calamos portfolio management teams, as well as a listing of portfolio holdings, financial statements and highlights, and detailed information about the performance and positioning of the Calamos Fund.

Finding Stable Income in a Low-Yield, High-Volatility World

For many, this appears a tall order. Traditional bond funds and passive strategies such as ETFs are likely to face headwinds in a volatile, low-rate environment. However, I believe Calamos closed-end funds are well positioned to address the search for stable income in a low yield, high volatility world. The funds are differentiated by their dynamic allocation and multi-asset class approaches, which offer considerable potential benefits for investors seeking income and capital appreciation. What’s more, our funds are actively managed and can adjust to the changing risks and opportunities in the market.

On April 1, 2020, we announced that the Fund had transitioned from a managed distribution to a level rate distribution plan effective as of March 31, 2020. This change had no impact on the Fund’s distribution rate. We believe the change allows CHW to maintain a stable level distribution sustainable over the long-term. During the period, the Fund provided a compelling monthly distribution of $0.0700 per share. We believe the Fund’s current annualized distribution rate, which was 12.18%* on a market price basis as of April 30, 2020, was very competitive, given the low interest rates in many segments of the bond market.

We understand that many closed-end fund investors seek steady, predictable distributions. With the Fund’s level rate distribution policy, we aim to keep distributions consistent from month to month, and at a level that we believe can be sustained over the long term. In setting the Fund’s distribution rate, the investment management team and the Fund’s Board of Trustees consider the interest rate, market and economic environment. We also factor in our assessments of individual securities and asset classes.

*Current Annualized Distribution Rate is the Fund’s most recent distribution, expressed as an annualized percentage of the Fund’s current market price per share. The Fund’s 4/30/20 distribution was $0.0700 per share. Based on our current estimates, we anticipate that approximately $0.0013 is paid from ordinary income or net realized short-term capital gains and that approximately $0.0687 represents a return of capital. Estimates are calculated on a tax basis rather than on a generally accepted accounting principles (GAAP) basis, but should not be used for tax reporting purposes. Distributions are subject to re-characterization for tax purposes after the end of the fiscal year. This information is not legal or tax advice. Consult a professional regarding your specific legal or tax matters. Under the Fund’s level rate distribution policy, distributions paid to common shareholders may include net investment income, net realized short-term capital gains and return of capital. When the net investment income and net realized short-term capital gains are not sufficient, a portion of the distribution will be a return of capital. The distribution rate may vary.

2   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

Market Review

The semiannual period brought unprecedented uncertainty to the global economy and markets. Global efforts to contain the COVID-19 pandemic resulted in severe and rapid declines in economic activity and global financial markets. The turmoil in the markets reached its height in March, with the S&P 500 falling more than 30% over just a few weeks. As investors sought safe havens and central banks lowered short-term rates, yields plummeted and the U.S. 10-year Treasury yield reached a record low. Meanwhile, oil prices slumped on the back of weak demand and geopolitics. By the end of the reporting period, market conditions had stabilized to a large extent, however. Significant market rebounds occurred during the final weeks of the period as investor sentiment improved in the wake of fiscal and monetary policy efforts.

For the semiannual period overall, equities came under the most pressure, particularly emerging market equities. Convertible securities demonstrated relative resilience, with the U.S. market posting a modest advance and the global market falling slightly. In the bond market, U.S. investment grade and short-term U.S. markets gained, benefiting from a flight to perceived safety.¹

Outlook

We are confident that both the economy and markets will recover, although we cannot predict the exact timeline. Although we are in the midst of sweeping uncertainties and discouraging headlines, it is important to remember that the economy and markets have navigated many crises that seemed quite insurmountable at the time.

Countries around the world have responded to the pandemic with unprecedented global monetary and fiscal policy responses. In the U.S., the Federal Reserve and federal government have acted swiftly, increasing the likelihood for a relatively faster economic recovery. U.S. consumer balance sheets are in better shape than they were in 2008, while credit markets and the banking system are operating in an orderly fashion.

From an investment perspective, the economy and markets are unlikely to recover at the same pace. Markets are typically forward looking and have often turned the corner not when problems were fully solved but when things looked “less bad.” We’ve already seen the stock market gain ground back from March lows, and we believe better market conditions can continue, even before the pandemic is resolved and the economy is fully up and running again.

Even though market conditions have improved since late March, we expect volatility to remain very high, due to the pandemic, economic shocks and U.S. elections. This is an environment that will favor active management and security selection. As conditions change, we may see significant shifts in market leadership. We believe that our investment teams will be able to navigate these crosscurrents, drawing on our long-term perspective, risk-management experience and deep research capabilities.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   3

Throughout my 50-year investing career, I have maintained that there is opportunity in every market environment. I believe this holds true. During this recent correction, many securities were sold off more severely than we believe their fundamentals warranted. Our teams sought to take advantage of these dislocations to build positions in companies, sectors and investment themes that provide attractive compensation for their potential risks. Additionally, our teams are finding many opportunities in newly issued securities. For example, as companies seek capital, high yield bonds and convertible securities are coming to market with very attractive terms.

Asset Allocation Considerations for Investors: Stay Invested and Utilize Calamos Closed-End Funds

As the global health crisis of COVID-19 has upended the global economy, many investors are understandably worried about their asset allocations. In these fast moving markets, making panicked moves or trying to time the markets is very dangerous. Markets can rise as unpredictably as they fall, but it’s impossible to predict these changes with certainty. Investors who make sudden shifts when markets are falling may find that they’ve capture the downside, only to miss the upside.

For decades, Calamos Investments has been dedicated to helping investors pursue their financial goals, including through uncertain environments. Now more than ever during this crisis, we believe the case is strong for staying invested and utilizing Calamos closed-end funds.

Calamos closed-end funds have the flexibility to invest in a wide array of securities with income and appreciation potential. These include stocks, convertible securities, high yield bonds and preferred securities. These asset classes have been less dependent on interest rates to source income. Additionally, certain Calamos closed-end funds employ alternative strategies (such as long/short equity and options writing) to source income and total returns.

Calamos closed-end funds are designed to meet the needs of long-term investors. We understand the importance that clients place on risk management, and we continually seek out ways to enhance the risk/reward characteristics of the funds. For example, the Fund’s active management of convertible securities, which combine the characteristics of stocks and traditional fixed income securities, provided the opportunity for upside participation with equity risk mitigation on the downside in March.

Calamos closed-end funds help investors stay invested for the long-term—and avoid the dangerous temptation to time the markets. Far too often, investors who make lots of short-term moves get whipsawed—they sell at the lows and miss the rebounds. This short-term mindset can have a very detrimental impact on returns.

Of course we strongly encourage you to seek out your investment professional, who can help address financial goals and risk considerations, as well as decide which Calamos closed-end funds are most appropriate for your income needs. Or visit us at www.calamos.com to learn more.

4   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

Conclusion

I founded Calamos Investments more than 40 years ago, during the difficult financial markets of the 1970s. Throughout the years, the economic and investment landscape have changed dramatically against a backdrop of technological advancements and globalization. However, our vision has remained constant. We are dedicated to providing innovative investment approaches that help investors achieve their financial goals, including through uncertain times.

As always, we thank you for your continued trust.

Sincerely,

John P. Calamos, Sr.

Founder, Chairman and Global Chief Investment Officer

Before investing, carefully consider a fund’s investment objectives, risks, charges and expenses. Please see the prospectus containing this and other information or call 800.582.6959. Please read the prospectus carefully. Performance data represents past performance, which is no guarantee of future results. Current performance may be lower or higher than the performance quoted. Opinions are as of the publication date, subject to change and may not come to pass. Information is for informational purposes only and shouldn’t be considered investment advice.

Diversification and asset allocation do not guarantee a profit or protection against a loss.

1The MSCI All Country World Index is a measure of global stock market performance, which returned -7.43% for the six-month period ending April 30, 2020. The S&P 500 Index is an unmanaged index generally considered representative of the U.S. stock market. For the six-month period, the index returned -3.16%. The MSCI Emerging Market Index is a measure of emerging market equity performance. For the six-month period, the index returned -10.39%.

The ICE BofA All U.S. Convertibles Ex-Mandatory Index represents the U.S. convertible securities market excluding mandatory convertibles. The index returned 2.50% for the six-month period. The Refinitiv Global Convertible Bond Index is designed to broadly represent the global convertible bond market. The index returned -0.52% for six-month period.

The Bloomberg Barclays U.S. Aggregate Bond Index is considered generally representative of the investment-grade bond market. For the six-month period ending April 30, 2020, the index returned 4.86%. The Bloomberg Barclays U.S. High Yield 2% Issuer Capped Index measures the performance of high yield corporate bonds with a maximum allocation of 2% to any one issuer. The index returned -6.60% for the six-month period. The Bloomberg Barclays U.S. Government/Credit 1-3 Years Index includes all medium and larger issues of U.S. government, investment-grade corporate, and investment-grade international dollar-denominated bonds that have maturities of between 1 and 3 years and are publicly issued. The index returned 2.58% for the six-month period.

Source: Lipper, Inc. and Mellon Analytical Solutions, LLC. Unmanaged index returns assume reinvestment of any and all distributions and, unlike fund returns, do not reflect fees, expenses or sales charges. Investors cannot invest directly in an index. Investments in overseas markets pose special risks, including currency fluctuation and political risks. These risks are generally intensified for investments in emerging markets. Countries, regions, and sectors mentioned are presented to illustrate countries, regions, and sectors in which a fund may invest. Fund holdings are subject to change daily. The Funds are actively managed. The information contained herein is based on internal research derived from various sources and does not purport to be statements of all material facts relating to the securities mentioned. The information contained herein, while not guaranteed as to accuracy or completeness, has been obtained from sources we believe to be reliable. There are certain risks involved with investing in convertible securities in addition to market risk, such as call risk, dividend risk, liquidity risk and default risk, which should be carefully considered prior to investing.

This information is being provided for informational purposes only and should not be considered investment advice or an offer to buy or sell any security in the portfolio. Investments in alternative strategies may not be suitable for all investors.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   5

Enhanced Fixed Income and Total Return Strategies

Calamos closed-end funds draw upon decades of our pioneering experience, including a long history of opportunistically blending asset classes in an attempt to capture upside potential while seeking to manage downside risk. Our closed-end funds can be broadly grouped into two categories: enhanced fixed income and total return. The funds share a focus on producing income while offering exposure to various asset classes and sectors.

6   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

TOTAL RETURN* AS OF 4/30/20

SECTOR WEIGHTINGS

Sector Weightings are based on managed assets and may vary over time. Sector Weightings exclude any government/sovereign bonds or options on broad market indexes the Fund may hold.

GLOBAL DYNAMIC INCOME FUND (CHW)

INVESTMENT TEAM DISCUSSION

Please discuss the Fund’s strategy and role within an asset allocation.

Calamos Global Dynamic Income Fund (CHW) is a global enhanced fixed-income product that seeks to provide an attractive monthly distribution with a secondary objective of capital appreciation. We believe the Fund offers a diversified way to participate in the long-term potential of global markets.

In this portfolio, we draw upon our team’s wide-ranging experience in multiple asset classes. We utilize a highly flexible approach by investing in equities, convertible securities and high yield bonds. We may also employ a “covered call” strategy to both mitigate equity risk and enhance income opportunities. Through covered call writing, we seek to generate income by selling (“writing”) options on market indexes. We may also employ a convertible arbitrage alternative strategy, in which we invest in convertible securities and short sell the convertibles’ underlying equities to generate income and hedge against risk. The ability to access multiple investment strategies, sectors and regions, especially during times of market dislocation, offers tremendous advantages, as we seek to mitigate risk by avoiding overvalued areas, while seizing upon opportunities in undervalued spaces.

We believe that this broad mandate enhances our ability to capitalize on market volatility, manage potential downside risks and generate more income versus traditional fixed income funds. The allocation to each asset class and strategy is dynamic, reflecting our view of the economic landscape and the potential of individual securities. By combining asset classes and strategies, we have the ability to fine-tune our positioning to generate income and capital gains. The broader range of security types also provides us with increased opportunities to manage the risk/reward characteristics of the portfolio over full market cycles. For the period, our participation in equity markets was beneficial to the overall performance of the Fund.

We invest in both U.S. and non-U.S. companies, with at least 40% of assets invested in foreign corporations. We emphasize companies with reliable debt servicing, respectable balance sheets and sustainable prospects for growth. Regardless of a company’s country of domicile, we favor companies with geographically diversified revenue streams and global business strategies.

How did the Fund perform over the reporting period?

The Fund returned -9.05% on a net asset value (NAV) basis for the six-month period ended April 30, 2020. On a market price basis, the Fund returned -14.76%. For the sake of comparison with the broader global markets, the MSCI EAFE Index returned -14.00%, the MSCI World Index returned -7.03%, and the S&P 500 Index declined -3.16% during the period.

At the end of the reporting period, the Fund’s shares traded at a -3.55% discount to NAV.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   7

SINCE INCEPTION MARKET PRICE AND NAV HISTORY THROUGH 4/30/20

Performance data quoted represents past performance, which is no guarantee of future results. Current performance may be lower or higher than the performance quoted. The principal value of an investment will fluctuate so that your shares, when sold, may be worth more or less than their original cost. Returns at NAV reflect the deduction of the Fund’s management fee, debt leverage costs and all other applicable fees and expenses. You can obtain performance data current to the most recent month end by visiting www.calamos.com.

How do NAV and market price return differ?

Closed-end funds trade on exchanges, where the price of shares may be driven by factors other than the value of the underlying securities. Market price may be influenced by factors unrelated to the performance of the fund’s holdings, such as general market sentiment or future expectations. During periods of high market volatility, closed-end fund prices may disproportionately underperform relative to their underlying NAVs, as shareholders often times source them for liquidity purposes. A fund’s NAV return measures the actual return of the individual securities in the portfolio, less fund expenses. It also measures how a manager was able to capitalize on market opportunities. Because we believe closed-end funds are best utilized long-term within asset allocations, we think that NAV return is the better measure of a fund’s performance. However, when managing the fund, we strongly consider actions and policies that we believe will optimize its overall price performance and returns based on market price.

Please discuss the Fund’s distributions during the six-month period.

On April 1, 2020, the Fund announced the change to a “Level Rate Distribution Policy.” This change had no impact on the Fund’s distribution rate. We believe this change allows CHW to continue to maintain a stable level distribution sustainable over the long-term. In each month of the period, the Fund distributed $0.0700 per share, resulting in a current annualized distribution rate of 12.88% of market price as of April 30, 2020.

We believe that both the Fund’s distribution rate and level remained attractive and competitive, as low interest rates limited yield opportunities in much of the marketplace. For example, as of April 30, 2020, the dividend yield of S&P 500 Index stocks averaged approximately 2.16%. Yields also were low within the U.S. government bond market, with the 10-year U.S. Treasury and 30-year U.S. Treasury yielding 0.64% and 1.28%, respectively.

8   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

What factors influenced performance over the reporting period?

The outbreak of the COVID-19 virus had a devastating impact on financial markets and global economies, as all sectors comprising the MSCI ACWI Index reflected the very challenging conditions. On the policy front, the Federal Reserve took aggressive actions to support the economy and stabilize markets, including an emergency interest rate cut, increased repo operations and significant asset purchases in the open market. From a fiscal perspective, Congress approved a multi-trillion dollar stimulus package with provisions to help individuals, businesses and municipalities. U.S. economic readings indicated the rapid toll on economic activity, with consumer confidence and employment figures heading south following years of improvement over this extended cycle.

The Fund has the ability to invest in a range of strategies including convertible securities, high yield as well as U.S. and global equities. This enables the Fund to participate in a myriad of opportunities on behalf of our shareholders. Given this flexibility, we can attempt to mitigate financial markets’ risk from COVID-19 by adjusting our exposures across these multiple strategies. This flexibility should be helpful as we seek to mitigate risk in vulnerable areas of the financial markets, and take advantage of opportunities in the midst of economic recovery.

The Fund’s U.S. equity sleeve outperformed relative to the S&P 500 Index, as selection in financials (specifically avoiding regional banks) contributed to performance. In addition, our selection and underweight in real estate, namely no exposure to retail REITs, was additive.

Conversely, our selection in industrials (aerospace & defense) impeded performance relative to the index. In addition, our selection and underweight in information technology (specifically in technology hardware, storage & peripherals) was not helpful.

The Fund’s global equity sleeve outperformed relative to the MSCI World Index. Our selection and overweight in consumer discretionary, notably in automobile manufacturers, was helpful. Our selection and underweight in financials, namely in diversified banks, also proved beneficial.

Conversely, an overweight in multi-utilities within the utilities sector held back performance. In addition, our selection in information technology, specifically an underweight and selection in systems software, weighed on results.

The Fund’s international sleeve outperformed relative to the MSCI EAFE Index. Our overweight and selection in materials, namely gold, was beneficial relative to the index. An overweight and selection in communication services, in interactive home entertainment in particular, was also helpful. From a regional standpoint, an overweight allocation and security selection in the U.S. added value. In addition, the Fund benefitted from favorable security selection in Emerging Asia.

Conversely, an overweight and selection in health care, specifically in pharmaceuticals, impeded performance relative to the MSCI EAFE Index. In addition, our overweight in energy, notably in oil & gas drilling, hindered returns. From a regional perspective, an underweight toward Japan detracted from relative performance. In addition, selection in EMEA lagged.

Convertible Arbitrage entails owning a convertible bond long and then shorting its underlying stock. It is employed as a strategy to enhance returns. The strategy benefitted from increasing volatility, though this benefit was offset somewhat by widening credit spreads. According to Bloomberg Barclays, high yield credit spreads widened from 415 basis points to 766 basis points during the six-month period.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   9

During the period, we were able to invest in robust new convertible issuance that offered favorable terms and valuations. Per ICE BofA, the U.S. has seen $26.4 billion in new issuance so far in 2020 through April 30. Annualized, this would put 2020 U.S. issuance on track to exceed $79.2 billion and would be the highest annual issuance witnessed since 2007.

How is the Fund positioned?

Given the enormous pressure that companies are under because of the COVID-19 outbreak, we maintained a preference for larger-cap, growth-oriented companies with global presence and geographically diversified revenue streams. In keeping with an emphasis on risk management, we focus on companies that we believe have respectable balance sheets, solid free cash flows, and reliable debt servicing. We believe these qualities will be essential for companies to be successful going forward during the ultimate economic recovery.

Our heaviest allocations reside within the information technology, consumer services and financials sectors. We believe that these sectors should perform well as the market re-engages growth, and the U.S. consumer has more opportunities to access goods as the economy reopens. We also believe that businesses and individuals will remain focused on productivity enhancements in a post-Covid-19 environment, thereby stimulating demand for both technology and communication services. As an example, the contract tracing initiative presents opportunities in these sectors. We believe that financials remain an attractive sector, especially large-cap banks that have been able to weather the market disruptions and have the resources take advantage of recovery opportunities. With relatively high current yields, they also offer compelling income sources given the current low-interest-rate environment.

We see a return to growth regarding the global economy, as many countries revive from the paralysis of COVID-19. We maintain a heavier weighting in the U.S. where we favor quality growth companies with healthy balance sheets, strong brands, free cash flows and experienced management. We seek to invest in businesses poised to benefit from re-emergence of U.S. consumers with their optimism and spending power. We also see opportunities available outside the U.S., as Asia/Pacific and Europe each make up approximately 20% of our portfolio, and represent attractive valuations post COVID-19.

Conversely, our weights in real estate and utilities are notably below the index weighting, as we do not see these areas of the global economy realizing optimal growth.

The average credit quality of rated securities within the portfolio is approximately BB, which is higher than the Credit Suisse High Yield index. This is typical for the Fund, as our credit process tends to guide us away from the most speculative corporate securities. That said, we do selectively invest in lower-credit securities when we believe the risk/reward dynamics are favorable for our investors. Our holdings in credits that are CCC or below is approximately 4%.

As the financial markets begin to recover, we believe this environment is conducive to the prudent use of leverage as a means of enhancing total return and supporting the Fund’s distribution rate. With low current borrowing costs, our use of leverage may offer a favorable reinvestment dynamic as markets improve. As of April 30, 2020, our amount of leveraged assets was approximately 30%.

10   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

What are your closing thoughts for Fund shareholders?

Given our outlook for eventual recovery from the market lows of March, the Fund’s ability to invest in a myriad of securities that offer exposure to multiple sectors and global regions will be paramount as we seek to both mitigate risk and optimize opportunities for our shareholders

We believe that the U.S. consumer will once again prove to be the driving force for recovery in both the U.S. and global economies. Accordingly, we will keep that catalyst top of mind. We believe Fed actions and government fiscal policies will be extremely accommodative to economic recovery going forward. We are hopeful that we will begin to see a normalization of social activities later this year that will serve as a positive impetus to economic revitalization. To optimize returns, it is imperative to conduct an ongoing risk assessment during times of continued market volatility.

We must consider the coronavirus pandemic’s impacts on all aspects of economic activity, alongside policy actions and the path of corporate earnings, when analyzing global equities. Global monetary policy is extremely accommodative and the major central banks have taken aggressive actions to address the effects of reduced economic activity and heightened uncertainty. Against this challenging backdrop, we do see opportunities in global stocks, reflective of abundant global liquidity, a record level of coordinated stimulus, and the potential for virus mitigation and vaccine development. Despite these potential positives, we are mindful that markets will likely remain volatile, and we remain closely attuned to the near-term risks. We believe our active, risk-managed investment approach positions us to take advantage of the volatility, as well as opportunities in global equities and convertible securities.