FOR IMMEDIATE RELEASE

PROSPERITY BANCSHARES, INC.®

REPORTS FOURTH QUARTER

2022 EARNINGS

HOUSTON, January 25, 2023. Prosperity Bancshares, Inc.® (NYSE: PB), the parent company of Prosperity Bank® (collectively, “Prosperity”), reported net income of $137.9 million for the quarter ended December 31, 2022 compared with $126.8 million for the same period in 2021. Net income per diluted common share was $1.51 for the quarter ended December 31, 2022 compared with $1.38 for the same period in 2021, an increase of 9.4%, and the annualized return on fourth quarter average assets was 1.47%. Additionally, loans, excluding Warehouse Purchase Program and SBA Paycheck Protection Program (“PPP”) loans, increased $518.5 million or 3.0% (11.8% annualized) during the fourth quarter of 2022. Nonperforming assets remain low at 0.08% of fourth quarter average interest-earning assets.

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“During the fourth quarter of 2022, Prosperity continued to see growth in loans, which we expect will continue in 2023. The growth comes from new loans as well as existing loans not paying off as fast as they did when rates were low and it was opportunistic for borrowers to repay or move the loans. Consumer spending remains strong, especially in the tourism, restaurant and hospitality sectors. Real estate sales and pricing have been affected by the increase in rates, but we expect that because of inventory levels and population growth, the impact will be less in Texas and Oklahoma,” said David Zalman, Prosperity’s Senior Chairman and Chief Executive Officer.

"We believe that the economies in Texas and Oklahoma will outperform other states over the next several years as companies and individuals continue to move to the states because of lower tax rates and a business-friendly political environment. We expect that companies will need more infrastructure and buildings and consumers will need more housing and places to spend their money, and both will need banks to finance the growth," continued Zalman.

"While the net interest margin at some banks has improved immediately because of higher rates, we expect Prosperity’s net interest margin to continue to increase over the next several years as our bond portfolio, which yielded 1.96% during the fourth quarter of 2022, reprices to higher yields assuming that rates normalize near the current rate," concluded Zalman.

Results of Operations for the Three Months Ended December 31, 2022

Net income was $137.9 million(2) for the three months ended December 31, 2022 compared with $126.8 million(3) for the same period in 2021, an increase of $11.1 million or 8.7%. The change was primarily due to an increase in loans and securities interest income, partially offset by a decrease in PPP fees and interest income of $8.5 million, a decrease in loan discount accretion of $4.5 million, and an increase in interest expense. Net income per diluted common share was $1.51 for the three months ended December 31, 2022 compared with $1.38 for the same period in 2021, an increase of 9.4%. On a linked quarter basis, net income was $137.9 million(2) for the three months ended December 31, 2022 compared with $135.8 million(4) for the three months ended September 30, 2022, an increase of $2.1 million or 1.5%. The change was primarily due to an increase in noninterest income and a decrease in noninterest expense, partially offset by a decrease in net interest income. Net income per diluted common share was $1.51 for the three months ended December 31, 2022 compared with $1.49 for the three months ended September 30, 2022, an increase of 1.3%. Annualized returns on average assets, average common equity and average tangible common equity for the three months ended December 31, 2022 were 1.47%, 8.26% and 16.26%(1), respectively. Prosperity’s efficiency ratio (excluding net gains and losses on the sale or write down of assets and securities) was 40.87%(1) for the three months ended December 31, 2022.

Net interest income before provision for credit losses for the three months ended December 31, 2022 was $256.1 million compared with $244.8 million for the same period in 2021, an increase of $11.4 million or 4.6%. The change was primarily due to an increase in the average balances and average rates on loans held for investment and on investment securities, partially offset by a decrease in PPP fees and interest income of $8.5 million, a decrease in loan discount accretion of $4.5 million and an increase in the average rates on interest-bearing liabilities. On a linked quarter basis, net interest income before provision for credit losses was $256.1 million compared with $260.7 million for the three months ended September 30, 2022, a decrease of $4.5 million or 1.7%.

The net interest margin on a tax equivalent basis was 3.05% for the three months ended December 31, 2022 compared with 2.97% for the same period in 2021. The change was primarily due to an increase in the average balances and average rates on loans held for investment and on investment securities, partially offset by a decrease in PPP fees and interest income of $8.5 million, a decrease in loan discount accretion of $4.5 million and an increase in the average rates on interest-bearing liabilities. On a linked quarter basis, the net interest margin on a tax equivalent basis was 3.05% for the three months ended December 31, 2022 compared with 3.11% for the three months ended September 30, 2022. The linked quarter decrease was primarily due to an increase in the average rates on interest-bearing liabilities, partially offset by higher average balances and higher average rates on loans and average rates on investment securities.

Noninterest income was $37.7 million for the three months ended December 31, 2022 compared with $35.8 million for the same period in 2021, an increase of $2.0 million or 5.5%. This change was primarily due to a higher net gain on sale or write-down of

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assets, an increase in trust income and an increase in other noninterest income. On a linked quarter basis, noninterest income was $37.7 million compared with $34.7 million for the three months ended September 30, 2022, an increase of $3.0 million or 8.8%, primarily due to a higher net gain on the sale or write-down of assets and an increase in other noninterest income.

Noninterest expense was $119.2 million for the three months ended December 31, 2022 compared with $119.5 million for the same period in 2021, a decrease of $294 thousand. On a linked quarter basis, noninterest expense decreased $3.0 million or 2.4% to $119.2 million compared with $122.2 million for the three months ended September 30, 2022. This change was primarily due to a decrease in salaries and benefits, partially offset by an increase in other noninterest expense.

Results of Operations for the Year Ended December 31, 2022

Net income was $524.5 million(5) for the year ended December 31, 2022 compared with $519.3 million(6) for 2021, an increase of $5.2 million or 1.0%. Net income per diluted common share was $5.73 for the year ended December 31, 2022 compared with $5.60 for 2021, an increase of 2.3%. Annualized returns on average assets, average common equity and average tangible common equity for the year ended December 31, 2022 were 1.39%, 7.97% and 15.94%(1), respectively. Prosperity’s efficiency ratio (excluding net gains and losses on the sale or write down of assets and securities) was 42.23%(1) for the year ended December 31, 2022.

Net interest income before provision for credit losses for the year ended December 31, 2022 was $1.005 billion compared with $993.3 million for the prior year, an increase of $11.9 million or 1.2%. The change was primarily due to an increase in average balances and average rates on investment securities, partially offset by a decrease in PPP fees and interest income of $44.6 million, a decrease in loan discount accretion of $31.9 million and an increase in the average rates on interest-bearing liabilities.

The net interest margin on a tax equivalent basis for the year ended December 31, 2022 was 3.00% compared with 3.14% for 2021. The change was primarily due to an increase in the average balances on investment securities, partially offset by a decrease in PPP fees and interest income of $44.6 million, a decrease in loan discount accretion of $31.9 million and an increase in the average rates on interest-bearing liabilities.

Noninterest income was $145.1 million for the year ended December 31, 2022 compared with $140.0 million for 2021, an increase of $5.2 million or 3.7%, primarily due to an increase in NSF income, a net gain on the sale or write-down of assets, an increase in trust income and an increase in other noninterest income, partially offset by a decrease in mortgage income.

Noninterest expense was $484.2 million for the year ended December 31, 2022 compared with $473.6 million for 2021, an increase of $10.6 million or 2.2%. The change was primarily due to an increase in salaries and benefits, an increase in credit and debit card and data processing expense and the change in net loss (gain) on sale or write-down of other real estate.

Balance Sheet Information

At December 31, 2022, Prosperity had $37.690 billion in total assets, a decrease of $144.1 million or 0.4%, compared with $37.834 billion at December 31, 2021.

Loans at December 31, 2022 were $18.840 billion, an increase of $223.7 million or 1.2%, compared with $18.616 billion at December 31, 2021, primarily due to increases in 1-4 family residential and construction, land development and other land loans, partially offset by decreases in Warehouse Purchase Program, PPP and commercial real estate loans. Linked quarter loans increased $333.5 million or 1.8% (7.2% annualized) from $18.506 billion at September 30, 2022. Excluding Warehouse Purchase Program and PPP loans, loans at December 31, 2022 were $18.093 billion compared to $16.671 billion at December 31, 2021, an increase of $1.422 billion or 8.5%. Linked quarter loans, excluding Warehouse Purchase Program and PPP loans, increased $518.5 million or 3.0% (11.8% annualized) from $17.575 billion at September 30, 2022.

As part of its lending activities, Prosperity extends credit to oil and gas production and servicing companies. Oil and gas production loans are loans to companies directly involved in the exploration and/or production of oil and gas. Oil and gas servicing loans are loans to companies that provide services for oil and gas production and exploration. At December 31, 2022, oil and gas loans totaled $429.5 million (net of discount and excluding PPP loans totaling $3.4 million) or 2.3% of total loans, of which $209.0 million were production loans and $220.5 million were servicing loans, compared with total oil and gas loans of $491.3 million (net of discount and excluding PPP loans totaling $27.9 million) or 2.6% of total loans at December 31, 2021, of which $294.1 million were production loans and $197.2 million were servicing loans. In addition, as of December 31, 2022, Prosperity had total unfunded commitments to oil and gas companies of $453.4 million compared with total unfunded commitments to oil and gas companies of $419.0 million as of December 31, 2021. Unfunded commitments to producers include letters of credit issued in lieu of oil well plugging bonds.

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Deposits at December 31, 2022 were $28.534 billion, a decrease of $2.238 billion or 7.3%, compared with $30.772 billion at December 31, 2021, primarily due to a decrease in public fund deposits. Linked quarter deposits decreased $766.6 million or 2.6% from $29.300 billion at September 30, 2022.

Asset Quality

Nonperforming assets totaled $27.5 million or 0.08% of quarterly average interest-earning assets at December 31, 2022 compared with $28.1 million or 0.09% of quarterly average interest-earning assets at December 31, 2021 and $19.9 million or 0.06% of quarterly average interest-earning assets at September 30, 2022.

The allowance for credit losses on loans and off-balance sheet credit exposures was $311.5 million at December 31, 2022 compared with $316.3 million at December 31, 2021 and $312.1 million at September 30, 2022. There was no provision for credit losses for the three months and years ended December 31, 2022 and 2021.

The allowance for credit losses on loans was $281.6 million or 1.49% of total loans at December 31, 2022 compared with $286.4 million or 1.54% of total loans at December 31, 2021 and $282.2 million or 1.52% of total loans at September 30, 2022. Excluding Warehouse Purchase Program and PPP loans, the allowance for credit losses on loans to total loans was 1.56%(1) at December 31, 2022 compared with 1.72%(1) at December 31, 2021 and 1.61%(1) at September 30, 2022.

Net charge-offs were $603 thousand for the three months ended December 31, 2022 compared with net charge-offs of $807 thousand for the three months ended December 31, 2021 and net charge-offs of $1.8 million for the three months ended September 30, 2022. During the fourth quarter of 2022, net charge-offs did not include any purchased credit deteriorated (“PCD”) loans and $6.2 million of specific reserves on resolved PCD loans was released to the general reserve.

Net charge-offs were $4.8 million for the year ended December 31, 2022 compared with $29.7 million for the year ended December 31, 2021. Net charge-offs for the year ended December 31, 2022 did not include any PCD loans and $8.2 million of specific reserves on resolved PCD loans was released to the general reserve during the period.

Dividend

Prosperity Bancshares declared a first quarter 2023 cash dividend of $0.55 per share to be paid on April 3, 2023, to all shareholders of record as of March 15, 2023.

Stock Repurchase Program

On January 17, 2023, Prosperity Bancshares announced a stock repurchase program under which up to 5%, or approximately

4.6 million shares, of its outstanding common stock may be acquired over a one-year period expiring on January 17, 2024, at the discretion of management. Under its 2022 stock repurchase program, Prosperity Bancshares repurchased zero shares of its common stock during the three months ended December 31, 2022 and 981,884 shares of its common stock at an average weighted price of $66.90 per share during the year ended December 31, 2022.

Pending Acquisition of First Bancshares of Texas, Inc.

On October 11, 2022, Prosperity Bancshares and First Bancshares of Texas, Inc. (“First Bancshares”) jointly announced the signing of a definitive merger agreement whereby First Bancshares, the parent company of FirstCapital Bank of Texas, N.A. (“FirstCapital Bank”) will merge with and into Prosperity. FirstCapital Bank operates 16 full-service banking offices in 6 different markets in West, North and Central Texas areas, including its main office in Midland, and banking offices in Midland, Lubbock, Amarillo, Wichita Falls, Burkburnett, Byers, Henrietta, Dallas, Horseshoe Bay, Marble Falls and Fredericksburg, Texas. As of September 30, 2022, First Bancshares, on a consolidated basis, reported total assets of $2.203 billion, total loans of $1.631 billion and total deposits of $1.842 billion.

Under the terms of the merger agreement, Prosperity will issue 3,583,370 shares of Prosperity common stock plus $93.4 million in cash for all outstanding shares of First Bancshares capital stock, subject to certain conditions and potential adjustments. Based on Prosperity’s closing price of $69.27 on October 7, 2022, the total consideration was valued at approximately $341.6 million. The transaction is subject to customary closing conditions, including the receipt of regulatory approvals and approval of the shareholders of First Bancshares. The transaction is expected to close during the first half of 2023, although delays could occur.

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Pending Acquisition of Lone Star State Bancshares, Inc.

On October 11, 2022, Prosperity Bancshares and Lone Star State Bancshares, Inc. (“Lone Star”) jointly announced the signing of a definitive merger agreement whereby Lone Star, the parent company of Lone Star State Bank of West Texas (“Lone Star Bank”) will merge with and into Prosperity. Lone Star Bank operates 5 banking offices in the West Texas area, including its main office in Lubbock, and 1 banking center in each of Brownfield, Midland, Odessa and Big Spring, Texas. As of September 30, 2022, Lone Star, on a consolidated basis, reported total assets of $1.387 billion, total loans of $940.5 million and total deposits of $1.249 billion.

Under the terms of the merger agreement, Prosperity will issue 2,376,182 shares of Prosperity common stock plus $64.1 million in cash for all outstanding shares of Lone Star capital stock, subject to certain conditions and potential adjustments. Based on Prosperity’s closing price of $69.27 on October 7, 2022, the total consideration was valued at approximately $228.7 million. The transaction is subject to customary closing conditions, including the receipt of regulatory approvals and approval of the shareholders of Lone Star. The transaction is expected to close during the first half of 2023, although delays could occur.

Conference Call

Prosperity’s management team will host a conference call on Wednesday, January 25, 2023, at 11:30 a.m. Eastern Time (10:30 a.m. Central Time) to discuss Prosperity’s fourth quarter 2022 earnings. Individuals and investment professionals may participate in the call by dialing 877-883-0383 for domestic participants, or 412-902-6506 for international participants. The participant elite entry number is 6262776.

Alternatively, individuals may listen to the live webcast of the presentation by visiting Prosperity’s website at www.prosperitybankusa.com. The webcast may be accessed from Prosperity’s home page by selecting “Presentations, Webcasts & Calls” from the menu on the Investor Relations link and following the instructions.

Non-GAAP Financial Measures

Prosperity’s management uses certain non-GAAP financial measures to evaluate its performance. Specifically, Prosperity reviews return on average tangible common equity; tangible book value per share; the tangible equity to tangible assets ratio; allowance for credit losses on loans to total loans excluding Warehouse Purchase Program and PPP loans; and the efficiency ratio excluding net gains and losses on the sale or write down of assets and securities, for internal planning and forecasting purposes. Prosperity believes these non-GAAP financial measures provide information useful to investors in understanding Prosperity’s financial results and their presentation, together with the accompanying reconciliations, provides a more complete understanding of factors and trends affecting Prosperity’s business and allows investors to view performance in a manner similar to management, the entire financial services sector, bank stock analysts and bank regulators. Further, Prosperity believes that these non-GAAP financial measures provide useful information by excluding certain items that may not be indicative of its core operating earnings and business outlook. These non-GAAP financial measures should not be considered a substitute for, nor of greater importance than, GAAP basis financial measures and results; Prosperity strongly encourages investors to review its consolidated financial statements in their entirety and not to rely on any single financial measure. Because non-GAAP financial measures are not standardized, it may not be possible to compare these financial measures with other companies’ non-GAAP financial measures having the same or similar names. Please refer to the “Notes to Selected Financial Data” at the end of this Earnings Release for a reconciliation of these non-GAAP financial measures to the nearest respective GAAP financial measures.

Prosperity Bancshares, Inc. ®

As of December 31, 2022, Prosperity Bancshares, Inc.® is a $37.690 billion Houston, Texas based regional financial holding company providing personal banking services and investments to consumers and businesses throughout Texas and Oklahoma. Founded in 1983, Prosperity believes in a community banking philosophy, taking care of customers, businesses and communities in the areas it serves by providing financial solutions to simplify everyday financial needs. In addition to offering traditional deposit and loan products, Prosperity offers digital banking solutions, credit and debit cards, mortgage services, retail brokerage services, trust and wealth management, and treasury management.

Prosperity currently operates 272 full-service banking locations: 65 in the Houston area, including The Woodlands; 30 in the South Texas area including Corpus Christi and Victoria; 62 in the Dallas/Fort Worth area; 22 in the East Texas area; 29 in the Central Texas area including Austin and San Antonio; 34 in the West Texas area including Lubbock, Midland-Odessa and Abilene; 16 in the Bryan/College Station area; 6 in the Central Oklahoma area; and 8 in the Tulsa, Oklahoma area.

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Cautionary Notes on Forward-Looking Statements

“Safe Harbor” Statement under the Private Securities Litigation Reform Act of 1995: This release contains, and the remarks by Prosperity’s management on the conference call may contain, forward-looking statements within the meaning of the federal securities laws, including Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. From time to time, oral or written forward-looking statements may also be included in other information released to the public. Such forward-looking statements are typically, but not exclusively, identified by the use in the statements of words or phrases such as “aim,” “anticipate,” “believe,” “estimate,” “expect,” “goal,” “guidance,” “intend,” “is anticipated,” “is expected,” “is intended,” “objective,” “plan,” “projected,” “projection,” “will affect,” “will be,” “will continue,” “will decrease,” “will grow,” “will impact,” “will increase,” “will incur,” “will reduce,” “will remain,” “will result,” “would be,” variations of such words or phrases (including where the word “could,” “may,” or “would” is used rather than the word “will” in a phrase) and similar words and phrases indicating that the statement addresses some future result, occurrence, plan or objective. Forward-looking statements include all statements other than statements of historical fact, including forecasts or trends, and are based on current expectations, assumptions, estimates and projections about Prosperity Bancshares and its subsidiaries. These forward-looking statements may include information about Prosperity’s possible or assumed future economic performance or future results of operations, including future revenues, income, expenses, provision for loan losses, provision for taxes, effective tax rate, earnings per share and cash flows and Prosperity’s future capital expenditures and dividends, future financial condition and changes therein, including changes in Prosperity’s loan portfolio and allowance for loan losses, future capital structure or changes therein, as well as the plans and objectives of management for Prosperity’s future operations, future or proposed acquisitions, including the proposed transactions with First Bancshares and Lone Star, the future or expected effect of acquisitions on Prosperity’s operations, results of operations, financial condition, and future economic performance, statements about the anticipated benefits of each of the proposed transactions, and statements about the assumptions underlying any such statement, as well as expectations regarding the effects of the COVID-19 pandemic on Prosperity’s operating income, financial condition and cash flows. These forward‑looking statements are not guarantees of future performance and are based on expectations and assumptions Prosperity currently believes to be valid. Because forward-looking statements relate to future results and occurrences, many of which are outside of Prosperity’s control, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict. Many possible events or factors could adversely affect the future financial results and performance of Prosperity, First Bancshares, Lone Star or the combined company and could cause those results or performance to differ materially from those expressed in or implied by the forward-looking statements. Such risks and uncertainties include, among others: the occurrence of any event, change or other circumstance that could give rise to the right of a party to terminate the merger agreement with First Bancshares or Lone Star, as applicable, the outcome of any legal proceedings that may be instituted against Prosperity, First Bancshares or Lone Star, delays in completing either of the transactions, the failure to obtain necessary regulatory approvals (and the risk that such approvals may result in the imposition of conditions that could adversely affect the combined company or the expected benefits of each of the transactions) or First Bancshares shareholder approval or Lone Star shareholder approval or to satisfy any of the other conditions to the transactions on a timely basis or at all, the possibility that the anticipated benefits of the transactions are not realized when expected or at all, including as a result of the impact of, or problems arising from, the integration of the two companies or as a result of the strength of the economy and competitive factors generally, or specifically in the West Texas area and the West, North and Central Texas area where First Bancshares and Lone Star, respectively, do a majority of their respective business and Prosperity has a significant presence, the possibility that the transactions may be more expensive to complete than anticipated, including as a result of unexpected factors or events, diversion of management’s attention from ongoing business operations and opportunities, potential adverse reactions or changes to business or employee relationships, including those resulting from the announcement or completion of the transactions, Prosperity’s ability to complete the acquisition and integration of First Bancshares and of Lone Star successfully, and the dilution caused by Prosperity’s issuance of additional shares of its common stock in connection with the transactions. Prosperity disclaims any obligation to update such factors or to publicly announce the results of any revisions to any of the forward-looking statements included herein to reflect future events or developments. These and various other factors are discussed in Prosperity’s Annual Report on Form 10-K for the year ended December 31, 2021, and other reports and statements Prosperity has filed with the Securities and Exchange Commission (“SEC”). Copies of the SEC filings for Prosperity may be downloaded from the Internet at no charge from http://www.prosperitybankusa.com.

Additional Information about the First Bancshares Merger and Where to Find It

In connection with the proposed merger of First Bancshares into Prosperity, Prosperity has filed with the SEC a registration statement on Form S-4 to register the shares of Prosperity common stock to be issued to the shareholders of First Bancshares. The registration statement includes a preliminary proxy statement/prospectus. The definitive proxy statement/prospectus will be sent to the shareholders of First Bancshares seeking their approval of the proposed transaction.

WE URGE INVESTORS AND SECURITY HOLDERS TO READ THE REGISTRATION STATEMENT ON FORM S-4, THE PROXY STATEMENT/PROSPECTUS INCLUDED WITHIN THE REGISTRATION STATEMENT ON FORM S-4 AND ANY OTHER RELEVANT DOCUMENTS TO BE FILED WITH THE SECURITIES AND EXCHANGE COMMISSION IN

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CONNECTION WITH THE PROPOSED TRANSACTION BECAUSE THEY CONTAIN IMPORTANT INFORMATION ABOUT PROSPERITY, FIRST BANCSHARES AND THE PROPOSED TRANSACTION.

Investors and security holders may obtain free copies of these documents through the website maintained by the SEC at http://www.sec.gov. You will also be able to obtain these documents, when they are filed, free of charge, from Prosperity at http://www.prosperitybankusa.com. Copies of the proxy statement/prospectus can also be obtained, when it becomes available, free of charge, by directing a request by telephone or mail to Prosperity Bancshares, Inc., Prosperity Bank Plaza, 4295 San Felipe, Houston, Texas 77027 Attn: Investor Relations, (281) 269-7199 or to First Bancshares of Texas, Inc., 310 West Wall Street, Suite 1200, Midland, Texas 79701, Attention: Ken Burgess, (844) 322-8392.

Additional Information about the Lone Star Merger and Where to Find It

In connection with the proposed merger of Lone Star into Prosperity, Prosperity has filed with the SEC a registration statement on Form S-4 to register the shares of Prosperity common stock to be issued to the shareholders of Lone Star. The registration statement includes a preliminary proxy statement/prospectus. The definitive proxy statement/prospectus will be sent to the shareholders of Lone Star seeking their approval of the proposed transaction.

WE URGE INVESTORS AND SECURITY HOLDERS TO READ THE REGISTRATION STATEMENT ON FORM S-4, THE PROXY STATEMENT/PROSPECTUS INCLUDED WITHIN THE REGISTRATION STATEMENT ON FORM S-4 AND ANY OTHER RELEVANT DOCUMENTS TO BE FILED WITH THE SECURITIES AND EXCHANGE COMMISSION IN CONNECTION WITH THE PROPOSED TRANSACTION BECAUSE THEY CONTAIN IMPORTANT INFORMATION ABOUT PROSPERITY, LONE STAR AND THE PROPOSED TRANSACTION.

Investors and security holders may obtain free copies of these documents through the website maintained by the SEC at http://www.sec.gov. You will also be able to obtain these documents, when they are filed, free of charge, from Prosperity at http://www.prosperitybankusa.com. Copies of the proxy statement/prospectus can also be obtained, when it becomes available, free of charge, by directing a request by telephone or mail to Prosperity Bancshares, Inc., Prosperity Bank Plaza, 4295 San Felipe, Houston, Texas 77027 Attn: Investor Relations, (281) 269-7199 or to Lone Star State Bancshares, Inc., 6220 Milwaukee Avenue, Lubbock, Texas 79424, Attention: Alan Lackey, (806) 771-7717.

Participants in the Solicitation

Prosperity, First Bancshares and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the shareholders of First Bancshares in connection with the proposed transaction. Certain information regarding the interests of these participants and a description of their direct and indirect interests, by security holdings or otherwise, is included in the registration statement and proxy statement/prospectus regarding the proposed transaction and other relevant materials to be filed with the SEC when they become available.

Prosperity, Lone Star and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the shareholders of Lone Star in connection with the proposed transaction. Certain information regarding the interests of these participants and a description of their direct and indirect interests, by security holdings or otherwise, is included in the registration statement and proxy statement/prospectus regarding the proposed transaction and other relevant materials to be filed with the SEC when they become available.

Additional information about Prosperity and its directors and executive officers may be found in the definitive proxy statement of Prosperity relating to its 2022 Annual Meeting of Shareholders filed with the SEC on March 14, 2022, and other documents filed by Prosperity with the SEC. These documents can be obtained free of charge from the sources described above.

No Offer or Solicitation

This communication is for informational purposes only and is not intended to and does not constitute an offer to subscribe for, buy or sell, or the solicitation of an offer to subscribe for, buy or sell, or an invitation to subscribe for, buy or sell any securities or a solicitation of any vote or approval in any jurisdiction, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in which such offer, invitation, sale or solicitation would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended, and otherwise in accordance with applicable law.

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Prosperity Bancshares, Inc.®

Financial Highlights (Unaudited)

(In thousands)

(A) Includes $(4,396), $(296), $1,517, $2,115 and $2,290 in unrealized (losses) gains on available for sale securities for the quarterly periods ended December 31, 2022, September 30, 2022, June 30, 2022, March 31, 2022 and December 31, 2021, respectively.

(B) Includes $(3,473), $(234), $1,198 $1,671 and $1,809 in after-tax unrealized (losses) gains on available for sale securities for the quarterly periods ended December 31, 2022, September 30, 2022, June 30, 2022, March 31, 2022 and December 31, 2021, respectively.

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Prosperity Bancshares, Inc.®

Financial Highlights (Unaudited)

(In thousands)

(C) Interest income on securities was reduced by net premium amortization of $8,703, $9,947, $11,450, $12,857 and $16,006 for the three months ended December 31, 2022, September 30, 2022, June 30, 2022, March 31, 2022 and December 31, 2021, respectively, and $42,957 and $58,427 for the years ended December 31, 2022 and December 31, 2021, respectively.

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