EXHIBIT A JOINT FILING AGREEMENT

EXHIBIT A

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a statement on Schedule 13G (including amendments thereto) with respect to the Common Stock of Vaccinogen, Inc. and further agree that this agreement be included as an exhibit to such filing. Each party to the agreement expressly authorizes each other party to file on its behalf any and all amendments to such statement. Each party to this agreement agrees that this joint filing agreement may be signed in counterparts.

In evidence whereof, the undersigned have caused this Agreement to be executed on their behalf this 10^th day of February, 2017.

MPM BIOVENTURES III, L.P.
By:		MPM BioVentures III GP, L.P.,
		its General Partner
By:		MPM BioVentures III LLC,
		its General Partner
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Series A Member

MPM BIOVENTURES III-QP, L.P.
By:		MPM BioVentures III GP, L.P.,
		its General Partner
By:		MPM BioVentures III LLC,
		its General Partner
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Series A Member

MPM BIOVENTURES III, L.P.
By:		MPM BioVentures III GP, L.P.,
		its General Partner
By:		MPM BioVentures III LLC,
		its General Partner
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Series A Member

MPM BIOVENTURES III-QP, L.P.
By:		MPM BioVentures III GP, L.P.,
		its General Partner
By:		MPM BioVentures III LLC,
		its General Partner
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Series A Member

MPM BIOVENTURES III PARALLEL FUND, L.P.
By:		MPM BioVentures III GP, L.P.,
		its General Partner
By:		MPM BioVentures III LLC,
		its General Partner
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Series A Member

MPM BIOVENTURES III GMBH & CO. BETEILIGUNGS KG
By:		MPM BioVentures III GP, L.P.,
		in its capacity as the Managing Limited Partner
By:		MPM BioVentures III LLC,
		its General Partner
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Series A Member

MPM ASSET MANAGEMENT INVESTORS 2003 BVIII LLC
By:		/s/ Xxxx Xxxxx
		Name: Xxxx Xxxxx
		Title: Manager

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MPM BIOVENTURES III GP, L.P.						MPM BIOVENTURES III LLC
By:		MPM BioVentures III LLC,				By:		/s/ Xxxx Xxxxx
		its General Partner				Name:		Xxxx Xxxxx
						Title:		Series A Member
By:		/s/ Xxxx Xxxxx
Name:		Xxxx Xxxxx
Title:		Series A Member
By:		/s/ Xxxx Xxxxx				By:		/s/ Xxxxxxx Xxxxxxx
		Name: Xxxx Xxxxx						Name: Xxxxxxx Xxxxxxx

By:		/s/ Xxxxxxxx Xxxxxxxxx				By:		/s/ Xxxxxx Xxxxxx
		Name: Xxxxxxxx Xxxxxxxxx						Name: Xxxxxx Xxxxxx
By:		/s/ Xxxx Xxxxxxx				By:		/s/ Xxxxxxxx Xxxxx III
		Name: Xxxx Xxxxxxx						Name: Xxxxxxxx Xxxxx III

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MPM BIOVENTURES III GP, L.P.						MPM BIOVENTURES III LLC
By:		MPM BioVentures III LLC,				By:
		its General Partner				Name:		Xxxx Xxxxx
						Title:		Series A Member
By:
Name:		Xxxx Xxxxx
Title:		Series A Member

By:						By:
		Name: Xxxx Xxxxx						Name: Xxxxxxx Xxxxxxx

By:						By:
		Name: Xxxxxxxx Xxxxxxxxx						Name: Xxxxxx Xxxxxx

By:						By:
		Name: Xxxx Xxxxxxx						Name: Xxxxxxxx Xxxxx III

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