Exhibit 4.3

•••Industry Industria Canada Canada Canada Certificate of Amendment Certificat de modification Canada Business Corporations Act Lol canadienne sur les socletes par actions AETERNA ZENTARIS INC. Corporate name I Denomination socialc 264271-9 Corporation number I Numcro de societe I HEREBY CERTIFY that the articles of theJE CERTIFIE que les statuts de Ia societe above-named corporation are amended undersusmentionnee sont modifies aux termes de section 178 of the Canada Business !'article 178 de Ia Loi canadienne sur /es Corporations Act as set out in the attached societes par actions, tel qu'il est indique dans les articles of amendment. clauses modificatrices ci-jointes. Virginie Ethier Director I Directeur 2015-11-17 Date of Amendment (YYYY-MM-DD) Date de modification (MAA-MM-JJ)

1+1 Canada Industry lndustrie Canada Form4 Articles of Amendment Canada Business Corporations Act (CBCA) (s. 27 or 177) Formulaire 4 Clauses modificatrices Loi canadienne sur /es socif}tf}s par actions (LCSA) {at1. 27 ou 177) OJCorporate name Denomination sociale AETERNA ZENTARIS INC. 0Corporntion number Num<..de Ia societe 264271-9 [}] The articles arc amended as follows Les statuts sont modifies de Ia fa on sui\lante See attached schedule I Voir l'annexe ci-jointe [I}Declaration: I cenify that I am a di rector or an officer of the corporntion. Declaration :J'altestc que jc suis un admi nistrutcu r o u u n dirigca n t de Ia societe, Original signed by I Originalsigne par Philip A. Theodore Philip A. Theodore 843-900-3211 M1snpresentalJOft consut•esn ofTcncc and, an s\IJMW\ co1n1t'UCW\. apenan 11 lr•ble-lo • fine not nc.etdm& SSt;QJOt to impnsonman ror ••mn not atriAIIl\ mon\hs or both (s JI:ts«bon lS4l (lloCiheCIIC'Al s d d·.-empn fauer sc Mdantion eoN\IIUC me tnft¥Uon l't IQft aulcv IW d«<»J.Uon de culp.abiJut pal ptocidure tonwTUIR. at patlblt d \ftem.a.'unaJe deGOO rowamol dt"'mou.ou I"..,.do ca p<tnOS(p&rOIDIIh< 250(I)de lllCSAJ Y o .lt PfO\Idanllnf""""b'"' nq'"oed b) lhe CBCA Noto thM bolhlhe CIICA and lhe l'tllu.) A<HIIol\ lluunform.tlull\ IO be dudosod IO lh•l"'bh<. Ia '"" be Sloml '"pmon>lonfonn>UO<I bani. nUIIIber IC'IPPIMJ.I9 Vous f ssu des ......,pl<IMIIIJ cucb par lalCSA-II al•n-quo lalCSA d la l.ol ""I<> rmsct IMnll ('<WJNJ<IJ pmndl<nl quede lth ...,..."'""""IJ soiml do"il"" au1"'1>11<. lis .....,,11o<la d.1m II Nnqu.de '"""cr-"p<ftONids nllmbo IC'/PPlJ.(II9 Canada IC 3069 (2008104)

Schedule I Annexe Amendment Schedules I Annexes-ModHicdon The issued and outstanding common shares in the capital of the Corporation (each, a Common Share) are hereby consolidated on the basis of one (1) post-consolidation Common Share for each one hundred (100) pre-consolidation Common Shares. No fractionalCommon Shares shall be issued upon the consolidation of the issued and outstanding Common Shares in accordance with the foregoing. All new Common Shares to be issued upon the issuance of the Certificate of Amendment shall be rounded down to the nearest whole number of Common Shares and all fractional Common Shares to which a registered shareholder would otherwise become entitled as a result of the consolidation will be aggregated and sold by the Corporation's transfer agent and registrar on the market, with the net proceeds therefrom being proportionately distributed to registered shareholders.