Filed by Simmons First National Corporation

pursuant to Rule 425 under the

Securities Act of 1933, as amended,

and deemed filed pursuant to Rule 14a-12 under the

Securities Exchange Act of 1934, as amended

Subject Company: Spirit of Texas Bancshares, Inc.

Commission File Number: 001-38484

a'.1 1 Simmons .. B ank . PERSONAL h ome we lcome to s i mmo n s BUS I NESS Welcome to Simmons ABOU T OPE N A N AC CO UNT Abou t us W e hop e you ' ll t a ke so me t i me t o ge t f ami l ia r w i th th e m any pr ograms an d p er k s t ha t ma ke Simmons Ban k a grea t plac e t o work ! a Simmons Bank . MEMBER FDIC SPIRI T O F TEXAS -- BANK --- Since we fir st ope n ed for business i n P in e Bluff, Arkansas, in 1903, we've been ded i cated to working a l ongs id e l ocal ind i v idua ls and businesses i n t h e comm unit i es we callhome. Although our footprint now stretches across s i x s tate s and m o re than 200 l oca t ions, our co m mi tme n t to ou r cus t omers a nd commun it ies has not changed. T hro u ghou t t he u pcom ing tr ans it io n , we 'll be prov i ding reg u l a r upd ates h e re on th i s page. Should you ha ve any Hu man Resources questions , please co n tac t " A sk HR, " ou r one - stop HR re source a t ( 870 ) 541 - 113 7 o r AskHR @ s i mm on s b a n k . c o m . Culture o Cu l ture Co r n e r sto n es • Benefits o E m R I O Y .ee Bene fi ts G u i de • Programs o D eve l o R men t Pr og r ams o P ro f essio n a l Deve l oRme nt o U l t i mate You • Policies o Associate H a n dboo k Lear n more • N e w s R e l eases • Comm uni !'f . I n vo l veme n t • B ank Hol i da Y . s Schedule F or l>< - ,, 2021 BEST BANK S IN

Forwa r d - L ook i ng Statements Certain sta t ements con t ained in this co m municatio n may not be based o n h i s t orical fac t s and shou l d be considered " forward - look i ng statements • withi n the mean i ng o f the Priva t e Securities L i t igation Reform Act of 1995. T hese fo rw a rd - looking s t a t ements may be iden t ified by r eference to a future period{s) or by the use of forward - looking t e r minology , such as lt anticipa t e ,"" bel i eve ," H budget /'" co n temp l ate ,",, con t inue /' " estima t e ," " expect t r; foresee ;"" i n t end /'" i ndica t e ," " target ; " plan ," posit i ons ,"• p r ospects ,"" project ; " predic t ," or " p oten t ial ," by future conditiona l verbssuch as " cou l d ,"" may ,"• migh t ," " should ,"" w i ll," or " wo u ld ," or by variatio n s of such words or by s i m i l ar ex p ressio n s. T h ese forward - l ook i ng s t a t emen t s incl u de , withou t lim it a t i on , sta t ements re l a t ing t o t he impact Simmons First Nationa l Co r pora t ion { t he • company ") and Sp i rit o f Texas Ban c shares , I nc . ( " S p iri t " ) expect the proposed merger t r ansac t ion be t ween t he Company and Spi r i t ( " Proposed T ransaction " ) to have on the comb i ned e n t it ies ' ope r a t ions , financ i a l condit i on and financial res u lts , and t he Company ' s and Spiri t ' s expectations abo ut t he i r abili t y to obtain regula t ory approvals and Spirit ' s sha r eholder approva l , their ability t o successfully i ntegra t e the comb i ned bu sinesses and the amou nt of cost sav i ngs and o t her benefi t s t he Company and Spi r it expect t o rea l i ze as a re su l t of t he Proposed T r ansact i on. The fo r ward l ook i ng s t a t emen t s may also include, wi t hou t l i m it a t ion, t h ose re l at i ng to the Company ' s and Spir it ' s predic t ions o r expec t ations of fu t u r e bus i ness or financia l perfo rmance as well as goals and objectives for fu t u r e ope r a t i ons , financia l and bus i ness trends , bus i ness prospec t s, and management's ou t look or expectations for future g r owth, reven u e , expenses, assets, capital leve l s , l iq u idity levels , asset qual it y , profitability , earni n gs , acc r etion , cus t omer service, i nves t ment i n d i gital channels , o r o t he r f u t ure fi nanc i a l or bus i ness performance , s t r a t egies or expec t a t i ons , the impacts o f t he COV I D - 1 9 pandemic and t he abili t y of t he Company and Sp i r i t to manage the impacts o f t he COV I D - 1 9 pa ndemi c , capital resou r ces, ma r k e t r i sk , p l ans for investmen t s in secur i t ies , e ff ec t o f future l i tigation , acquisition s t rategy, legal and regula t o r y limita t i ons and comp l i ance and compe t i t ion . These forward - looking stateme n t s i nvolve r i sks and uncertain t ies , and may not be reali z ed due t o a varie t y o f factors , i ncluding , wi t hout l i mitation : changes in the Company ' s and Spi r i t ' s ope r a t ing, acq u is it ion , o r expansion s t rategy ; the effec t s o f future eco n om i c conditio n s {including unemp l oymen t l eve l s and s l owdowns in eco n om i c growth) , governme nt al monetary and fisca l po l ic i es , as well as l egislative and reg u l a t ory changes, including in response t o t he COVID - 19 pandem i c ; changes in i nte r est rates ; possible adverse rulings , j u dgemen t s , sett l emen t s, and o t her ou t comes of pending or fut ure l it i ga t i on; t he abil it y to obtain regu l a t o r y approvals and mee t o t her dosing conditions t o t he Proposed T ra n sact i on ; de l ay i n closing the Proposed Transac t i on ; difficu l t i es and de l ays in i ntegra ti ng t he Spirit business or fully realizing cos t savi n gs and o t he r benefi t s o f the Proposed Transac t ion; changes i n t he Compa n y ' s share price befo r e closing ; the outcomeo f a n y lega l proceedings that may be instituted aga i nst t he Company or Sp i r it as a r esu l t of t he Proposed Tr ansact i on or otherwise ; the occu r rence of any event , change or o t her c i r c u ms t ance that could give rise t o t he right of one o r bo t h par ti es to term i na t e the Agreemen t ; business disruption follow i ng t he Proposed T ransac t i on ; t he react i on to t he Proposed Transaction o f the companies ' cus t omers , employees and coun t erpa r ti es ; uncer t a i n t y as t o the exten t o f the duration , scope , and impac t s o f the COV I D - 1 9 pandemic on t he Company , Spiri t and t he Proposed T r ansaction ; and o t he r re l evan t r i sk factors, which may be detailed from time to t ime in t he Company ' s and Sp i rit ' s p r ess re l eases and fi lings with the U . S . Sec u ri t ies and Exchange Comm i ssion (the " S E C") . M any of t hese fac t ors a r e beyond the Company's and Sp i r it ' s ab i li t y to predic t or contro l , and actua l results co u ld d i ffer mater i ally from those in t he forward l ook i ng s t a t emen t s due t o t he se factors and others . In addi t i on, as a r esult of t hese and other fac t ors , the Company ' s a n d S p i r it ' s past fi nancia l performance shou l d not be rel i ed up o n as an in d i cation of future performance . The Company and Spi r it believe the ass u mptions and expec t a t ions t hat underl i e or a r e reflec t ed in any forward - looking statemen t s , exp r essed or implied , i n t h i s commu n i ca t ion are reasonable , based on information avai l ab l e to t he Company and Spirit on the da t e of this communica ti on . However, given t he described uncertain ti es and r isks, t he Company and Spi r i t canno t guarantee its future performance or resu lt s of operations or whether the Company ' s and Spir it ' s fu t u r e perfo rma n ce will differ ma t eria ll y from t he performance reflected in o r implied by it s forwa rd - l ook i ng statements , and yo u shou l d not place undue r eliance on these forwa r d - loo k ing statements . A ll forward - looking statements , expressed o r i mplied , i ncl u ded in this communica t ion a r e express l y qualified in their en t i re t y by the cautionary s t a t emen t s con t a i ned or re f erred to here i n. Any forward - look i ng statement s pea ks on l y as of the date of t h i s commun i cat i on , and nei t her t he Company nor Spir it undertakes any obl i ga t ion t o update o r revise any forward - l ook i ng statements , whe t he r as a result of new info r mation , fu t u r e even t s or o t her w i se .

I m po rt ant A dd i t i ona l I nfo r mation an d W here to Fin d I t Th i s comm u n i cation does not constit u t e an offe r to se ll or t he sol i ci t ation of an o ffer to b u y any secur i t i es or a so l i citat i on o f any vote or approval w it h respect to t he Proposed T ransaction . No offe r of secur i ties shall be made except by means of a pr ospectus meeting the requ i remen t s of t he Securities Act of 1 933 , as ame n ded , and no offe r to sell or solici t a t i on of an o ffer to buy shall be made in any j urisdiction in w h i c h such offer , so li citatio n or sale wou l d be unlawful. I n con n ec t i on with the P ro p osed Transac t i on , the Company w i ll fi l e with the S E C a registration statement on Fo rm S - 4 ( t he • Reg istration Sta t ement " ) t o regis t er the shareso f Company common stock t h at will be iss u ed t o Spi r i t share h o l ders in t he Proposed T ransaction . T he Registration Statement will include a proxy statemen t o f Sp i rit and a prospectus of t he Company (t he • P roxy Sta t ement / P r ospectus " ) , and t he Compa n y a n d / o r Spir i t may fi l e wit h t he SEC other r elevant documen t s concerning the P roposed Transaction . T he definitive P r oxy S t atemen t / Prospectus will be ma i l ed t o share h o l ders of S p i ri t . SHARE H O L DERS AR E URGED TO READ T HE REGISTRA TI O N STATEME NT AND T H E P ROXYS T A TE M E N T / PROSP E CTUS R E GARD I NG TH E PROPOSED TRANSACT I O N CARE F U LL Y AND I N IT S ENT IRETYW H EN IT B E CO M E S AVA I LABL E A N D ANY O T H E R R EL EVANT DOCUMENTS F I LEDW IT H T HESEC BY T HE CO MPAN Y AND / OR S P I R I T, ASWE LL AS ANY AM E N D M E N T S O R SUPPLEM E N T S TO T HOS E DOCUMENTS , B E CAUS E T H EY W I LL CO N T A I N IM P OR T AN T I N F ORMA T I ON ABOUTTHE PROPOSED TRANSAC TI O N . F ree copies of t h e P roxy Sta t ement / Prospectus , as well as ot he r fi l i n gs con t a i ni n g i nformat i on abo u t t he Company and Spirit, may be ob t a i ned at the S E C's I nterne t s it e (h.! tp :// www . sec . gov ) , when they are fi l ed by t he Company or S p i r it . You w i ll also beab l e to obtain these docume n t s , when t he y are fi l ed , free o f cha r ge, from t he Company a t simmonsbank.com un de r the head i n g " Investor Relations • or from Sp ir it a t www.so t b . com under t he " Investor Rela t i ons • l i n k . Co p ies of the Proxy Sta t ement / P r ospectus can also be obtained , when it becomes availab l e , freeo f charge , by direct i ng a r equest to the Company a t S i mmons F irst Na t i o na lCorporation, 501 M ain S t r ee t , Pine B l uff, Arkansas 71601, At t ention: Ed Bi l ek , Director of I nves t or Rel a t ions , Emai l : ed . b i l ek @ simmonsbank.com o r i r @ s i mmonsbank . com , Telephone: (870) 541 - 10 00; or by direct i ng a reques t to Spir it at Spi r i t ofTexas Bancsha re s, I nc. , 1836 Spi rit ofTexas Way, Co n roe, Texas 77301 , At t ention: Corpora t e Secretary , E mail: jgoleman @ so t b . com , Te lephone : (936) 521 - 1 836 . Participants i n the So l icitation The Company, Sp i r i t , and certain of t he i r r espec t ive direc t ors , executive office r s and emp l oyees may be deemed to be pa rtic i pan t s in t he so l ic it a t i on o f prox i es fro m the sha reh o l ders of Sp i ri t i n connec t i o n with the Proposed Transac t i on . I nforma t i on a b ou t the Com p any ' s d i rec t ors and execu t ive officers is availab l e in i t s pr oxy sta t ement fo r its 2021 annual meeting of sha reh o l ders , wh i ch was fi led with the S E C o n Apr i l15 , 2021 . Informa t ion about Sp i r it ' s d i rec t ors a n d execut i ve off i cers is avai l a b le i n i ts proxy s t atemen t for it s 202 1 annua l mee t ing o f shareholde rs , w h ich was filed wi t h t he SEC on April 9 , 2021 . I nformatio n regard i n g all o f the pers ons who may , unde r t he ru le s of t he SEC , be deemed par t icipants in t h e pr oxy so l ic i t a t i on a nd a descrip t ion of their d i rec t and in d i rec t interests , by security ho l d i ngs o r o t herwise , w i ll be con t ained in the Proxy S t a t ement/P r ospectus re gard i ng t he P r opose d T r ansact i on and o t he r re lev an t ma t erials t o be fi l ed with t he S E C when they become ava i lable . F re e cop i es of t hese documents may be obta i ned as de scribed in t he preceding paragraph.