Exhibit 5.1

                                  David E. Wise
                                 Attorney at Law
                            8794 Rolling Acres Trail
                          Fair Oaks Ranch, Texas 78015
                                 (830) 981-8165

                                  July 13, 2006

Colm King, President
Cavit Sciences, Inc.
100 E. Linton Boulevard, Suite 106B
Delray Beach, Florida 33483

Re: Cavit Sciences, Inc. - Registration Statement on Form SB-2

Dear Mr. King:

     We have acted as counsel to Cavit  Sciences,  Inc.,  a Florida  corporation
("Company"),  in connection  with a Registration  Statement on Form SB-2,  filed
with the  Securities  and Exchange  Commission  on July 13, 2006  ("Registration
Statement").  The Registration Statement covers 8,475,000 shares of Common Stock
("Common  Stock")  which  are  issuable  to the  shareholders  of Hard to  Treat
Diseases, Inc. in a spin-off transaction.

     In  rendering   this  opinion,   we  have  examined  (i)  the  Articles  of
Incorporation,  as amended, and By-Laws of the Company;  (ii) the resolutions of
the Board of Directors evidencing the corporate proceedings taken by the Company
to  authorize  the  original  issuance  of the  Common  Stock  to Hard to  Treat
Diseases,  Inc. and the  distribution  of such shares by Hard to Treat Diseases,
Inc. to its  shareholders  pursuant  to the  Registration  Statement;  (iii) the
Registration  Statement  (including all exhibits  thereto);  and (iv) such other
documents as we have deemed  appropriate or necessary as a basis for the opinion
hereinafter expressed.

     In  rendering  this  opinion,  we  have  assumed  the  genuineness  of  all
signatures and the authenticity of all documents submitted to us as certified or
photo static  copies.  As to questions of fact material to this  opinion,  where
such facts have not been  independently  established,  and as to the content and
form of the Articles of Incorporation and amendments thereto,  By-Laws, minutes,
records,  resolutions and other  documents and writings of the Company,  we have
relied to the extent we deem reasonably appropriate upon your representations or
certificates of officers or directors of the Company without  independent  check
or verification of their accuracy.

     Based  upon and  subject to the  foregoing,  and having due regard for such
legal  considerations  as we  deem  relevant,  we are of the  opinion  that  the
8,475,000  shares of common stock,  subject to  distribution as described in the
Registration  Statement,  and  subject  to  effectiveness  of  the  Registration
Statement  described above, the Common Stock will be legally issued,  fully paid
and nonassessable.

     We hereby  consent  to the  filing of this  opinion  as an  Exhibit  to the
Registration  Statement and to the reference made to this firm under the heading
"Legal Matters" in the Prospectus  contained in the  Registration  Statement and
all amendments thereto.

Sincerely,

/s/ David E. Wise
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David E. Wise, Attorney at Law