Document:

Exhibit 4.28

 

Letter of amendment
prepared and signed on July 24th 2012

to the letter of
undertaking signed by Audiocodes Ltd (hereinafter; “the

company”)
on December 12th 2011 in favour of Bank Leumi LeIsrael Ltd

(hereinafter: “the
bank”)

 

Whereas on December 12th 2011 the
company signed in favour of the bank on a letter of undertaking according to which the company made various undertakings vis-à-vis
the bank, all as detailed in the undertaking attached (hereinafter: “the letter of undertaking”)’

 

And whereas the parties have agreed to amend
the letter of undertaking as detailed hereinafter:

 

Therefore it is declared and agreed
between the parties as follows:

 

		1.	The preface to this letter of amendment constitutes an integral part of it thereof.

 

		2.	The aforementioned parties hereby agree that the letter of undertaking shall be amended as follows hereinafter:

 

		2.1.	Section 1 - under “profitability” - the sub-section hereinafter shall be added:

 

			1.8 The company’s operating profit accrued for four consecutive calendar quarters whereby the date of their termination
is the date of the last quarterly financial reports shall not be reduced by more than 15% of the forecasted operating profit that
the company presented in the attached appendix in regard to that same period, and the operating profit starting from March 31st
2013 shall be positive. To avoid doubt compliance with these undertakings shall also be examined on a quarterly basis.

 

    	 

    	 

    

 

			To avoid doubt it is hereby clarified that within the framework of the calculation of the operating profit expenses shall not
be taken into account for reduction of intangible assets and/or expenses up to a total of 3 million US dollars for accounting records
for the value of the benefit entailed in awarding options to employees pursuant to FAS123.

 

		2.2.	In Section 1 - following Section 1.8 - a new heading shall be added: “Financial ratios”.

 

		2.3.	In Section 1 - under “Financial ratios” - the following sub-section shall be added:

 

			1.9 The ratio between the company’s funds including cash and cash equivalents, short term and long term restricted bank
deposits, restricted bank deposits and long term marketable securities and the balance of the company’s undertakings vis-à-vis
banks, financial institutions, bond-holders and other lenders including the total undertakings bearing interest plus bank guarantees,
SBLC and documentary credit and so forth (without credit for request for securities for the purpose of protection transactions)
shall not be less at any time whatsoever than 1.35. To avoid doubt compliance with this undertaking shall also be examined on a
quarterly basis.

 

    	 

    	 

    

 

		3.	All the rest of the terms of the letter of undertaking shall remain fully valid and without any change.

 

	 	Yours sincerely,
	 	 
	Stamp:  	Audicodes Ltd
	 	Public Co. 520044132
	 	(signature)               (signature)
	 	Audiocodes Ltd

 

    	 

    	 

    

 

	 	 	2012A	 	 	2012A	 	 	2012E	 	 	2012E	 	 	Total	 	 	2013E	 	 	2013E	 	 	2013E	 	 	2013E	 	 	Total	 
	 	 	Q1-2012	 	 	Q2-2012	 	 	Q3-2012	 	 	Q4-2012	 	 	2012	 	 	Q1-2012	 	 	Q2-2013	 	 	Q3-2013	 	 	Q4-2013	 	 	2013	 
	Non GAAP Operating Income (Loss)	 	 	-981	 	 	 	-1,200	 	 	 	-2,450	 	 	 	-1,055	 	 	 	-5,698	 	 	 	28	 	 	 	613	 	 	 	1,198	 	 	 	1,490	 	 	 	33,28	 

 

	Stamp:  	Audicodes Ltd
	 	Public Co. 520044132
	 	(signature)               (signature)

 

    	 

    	 

    

 

Date: July 24th
2012

 

Att:

 

Audiocodes Ltd (“the company”)

 

Dear Sir or Madam,

 

Re: Letter of undertaking
dated December 12th 2011 (“Letter of

Undertaking”)

 

At your request we confirm that if the company
data, that shall be published within the framework of the company’s financial reports of June 30th 2012 and/or
September 30th 2012 and/or December 31st 2012 and/or December 31st 2013 and/or June 30th
2013 and/or September 30th 2013 (“the determining reports”) shall indicate non-compliance by the
company with the financial indices detailed in Section 1.7 of the letter of undertaking (“the agreed financial indices”),
we shall not realize our right to consign for immediate defrayal your debts and undertakings to us due to this.

 

This confirmation is restricted solely and
only to the aforementioned cause and it shall not derogate from our right to consign for immediate defrayal your debts and undertakings
for any other cause.

 

To avoid any doubt it is clarified that our
aforementioned waiver is a one-off waiver and relates to the determining reports only; our consent should not be considered to
be a waiver to your undertakings to comply with the agreed financial indices after the date of the determining reports, that is
after September 30th 2013, or as an amendment of the letter of undertaking, and all your undertakings as detailed in
the letter of undertaking shall remain in full force.

 

    	 

    	 

    

 

It is also clarified that our consent shall
not derogate from our rights to you pursuant to any document that you have signed and/or shall sign for us or pursuant to any law.

 

This letter shall be conditional on the following
terms:

 

		1.	You shall receive similar consent from anyone whose non-compliance with any financial indices whatsoever based on the aforementioned
determining reports award him the right for immediate defrayal of your debts and undertakings to them, including Bank Mizrahi Tefahot
Ltd and The First International Bank Ltd on condition that this consent shall not include conditions that are beneficial to that
same entity apart from that stated in this document.

 

		2.	You shall sign on a letter of amendment to the letter of undertaking which you signed on December 12th 2011 in the
attached wording.

 

		3.	A total of 1,000,000 US dollars shall be deposited in Account No. ######/## which shall be attached in favour of the bank by
a fixed first degree lien.

 

This letter shall come into force if by no
later than July 30th 2012 you shall pay us a total of NIS 100,000 for this letter, as has been agreed with you, and
you shall present to us a copy of this letter when it is signed by you in the margins.

 

    	 

    	 

    

 

Yours sincerely

 

Bank Leumi LeIsrael Ltd

 

We agree to the aforementioned

 

	Stamp:	Audicodes Ltd
	 	Public Co. 520044132
	 	(signature)               (signature)
	 	Customers’ SignatureExhibit 4.7

 

AMENDMENT NO. 1 TO 8% SENIOR CONVERTIBLE
DEBENTURE

 

THIS AMENDMENT NO.
1 TO 8% SENIOR CONVERTIBLE DEBENTURE (the “Amendment”) is entered into as of March ___, 2013 (the “Effective
Date”), by and between Arno Therapeutics, Inc. (the “Company”), and [_____________] (the “Holder”).

 

WHEREAS, the Company
issued the Holder that certain 8% Senior Convertible Debenture dated [November 26][December 18], 2012 (the “Debenture”);

 

WHEREAS, the Debenture
has a Maturity Date of [November 26][December 18], 2015, and provides for interest payments at the rate of 8% per annum, payable
quarterly in arrears beginning on January 1, 2013;

 

WHEREAS, the Company
and the Holder desire to amend the Debenture to provide for accrual of all interest payments until the Maturity Date.

NOW, THEREFORE, in
consideration of the mutual covenants and agreements contained herein, the parties hereby agree as follows:

 

1.Accrual of Interest. Section
2(a) of the Debenture is hereby amended and restated in its entirety as follows:

 

“(a)Payment of Interest
in Cash or Kind. Interest shall accrue hereunder at the rate of 8% per annum, compounding quarterly beginning on January 1,
2013, and each April 1, July 1, October 1 and January 1 thereafter. All accrued but unpaid interest shall be paid to the Holder
on the Maturity Date or, provided the Company shall have given the Holder at least 10 Trading Days’ prior written notice
in accordance with the notice requirements set forth below, on such earlier date or dates as determined by the Company in its sole
discretion (each such date, an “Interest Payment Date”) (if any Interest Payment Date is not a Business Day,
then the applicable payment shall be due on the next succeeding Business Day), in cash or, at the Company’s option, in duly
authorized, validly issued, fully paid and non-assessable shares of Common Stock at the Interest Conversion Rate (the dollar amount
to be paid in shares, the “Interest Share Amount”) or a combination thereof; provided, however,
that payment in shares of Common Stock may only occur if (i) on the Interest Payment Date and through and including the date such
shares of Common Stock are actually issued to the Holder all of the Equity Conditions have been met (unless waived by the Holder
in writing) and (ii) the Company shall have given the Holder at least 10 Trading Days’ prior written notice (the “Interest
Notice Period”) in accordance with the notice requirements set forth below and (iii) as to such Interest Payment Date,
prior to such Interest Notice Period (but not more than five (5) Trading Days prior to the commencement of such Interest Notice
Period), the Company shall have delivered to the Holder’s account with The Depository Trust Company a number of shares of
Common Stock to be applied against such Interest Share Amount equal to the quotient of (x) the applicable Interest Share Amount
divided by (y) the Interest Conversion Rate assuming for such purposes that the Interest Payment Date is the Trading Day immediately
prior to the commencement of the Interest Notice Period (the “Interest Conversion Shares”).”

    	 

    	 

    

 

2.Convertibility of Interest.
In order to clarify the parties’ understanding that, among other things, accrued but unpaid interest shall be convertible
by the Holder to the same extent as outstanding principal, the following definition of “Outstanding Amount” is hereby
added to Section 1 of the Debenture:

 

““Outstanding Amount”
shall mean the outstanding principal amount of this Debenture, plus all accrued and unpaid interest hereunder.”

 

In addition to the foregoing, Section 4(a)
of the Debenture is hereby amended and restated in its entirety as follows:

 

“(a) Voluntary Conversion.
At any time after the Original Issue Date until this Debenture is no longer outstanding, this Debenture shall be convertible, in
whole or in part, into shares of Common Stock at the option of the Holder, at any time and from time to time (subject to the conversion
limitations set forth in Section 4(d) hereof). The Holder shall effect conversions by delivering to the Company a written
notice, in substantially the form attached hereto as Annex A (each, a “Notice of Conversion”), specifying
therein the Outstanding Amount of this Debenture to be converted and the date on which such conversion shall be effected (such
date, the “Conversion Date”). If no Conversion Date is specified in a Notice of Conversion, the Conversion Date
shall be the date that such Notice of Conversion is deemed delivered hereunder. To effect conversions hereunder, the Holder shall
not be required to physically surrender this Debenture to the Company unless the entire principal amount of this Debenture, plus
all accrued and unpaid interest thereon, has been so converted. No ink-original Notice of Conversion shall be required, nor shall
any medallion guarantee (or other type of guarantee or notarization) of any Notice of Conversion form be required. Conversions
hereunder shall have the effect of lowering the Outstanding Amount of this Debenture in an amount equal to the applicable conversion,
with such reduction first being applied to accrued but unpaid interest. The Holder and the Company shall maintain records showing
the Outstanding Amount(s) converted and the date of such conversion(s). The Company may deliver an objection to any Notice of Conversion
within one (1) Business Day following the date such Notice of Conversion is deemed delivered. In the event of any dispute or discrepancy,
the records of the Holder shall be controlling and determinative in the absence of manifest error. The Holder, and any assignee
by acceptance of this Debenture, acknowledge and agree that, by reason of the provisions of this paragraph, following conversion
of a portion of this Debenture, the unpaid and unconverted principal amount of this Debenture may be less than the amount stated
on the face hereof.”

 

In addition, references to “principal
amount” and “outstanding principal amount” in the following sections of the Debenture shall be, and hereby are,
replaced with the term “Outstanding Amount”: (i) Section 2(c); (ii) Section 4(c)(i); (iii) Section 4(c)(iv); and, if
applicable, (iv) Section 4(d).

    	2

    	 

    

 

3.Revised Notice of Conversion.
In order to facilitate the foregoing, the form of Notice of Conversion attached to the Debenture as Annex A is hereby replaced
in its entirety with the revised form of Notice of Conversion attached hereto as Annex A.

 

4.Miscellaneous.
All capitalized terms used but not defined herein shall have the meanings ascribed to them in the Debenture. Except as amended
or modified by this Amendment, the parties hereby confirm all other terms and provisions of the Debenture. This Amendment may be
executed in any number of counterparts, each of which shall constitute an original, but all of which together shall constitute
one and the same instrument.

 

IN WITNESS WHEREOF, the undersigned have
executed this Amendment as of the date first written above.

 

	 	ARNO THERAPEUTICS, INC.
	 	 	 
	 	 	 
	 	By:	 
	 	Name: 	Glenn R. Mattes
	 	Title: 	President & Chief Executive Officer

 

 

 

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK

SIGNATURE PAGE FOR HOLDER FOLLOWS]

    	3

    	 

    

 

[holder
SIGNATURE PAGE TO 

AMENDMENT
No. 1 TO

8%
SENIOR CONVERTIBLE DEBENTURE]

 

IN WITNESS WHEREOF,
the undersigned have executed this Amendment as of the date first written above.

 

	Name of Holder:	 

 

	Signature of Authorized Signatory of Holder:	 

 

	Name of Authorized Signatory:	 

 

	Title of Authorized Signatory:	 

 

    	4

    	 

    

 

ANNEX A

 

NOTICE OF CONVERSION

 

The undersigned hereby
elects to convert some or all of the Outstanding Amount under the 8% Senior Convertible Debenture due [November 26][December 18],
2015 of ARNO THERAPEUTICS, INC., a Delaware corporation (the “Company”), into shares of common stock (the “Common
Stock”), of the Company according to the conditions hereof, as of the date written below. If shares of Common Stock are
to be issued in the name of a person other than the undersigned, the undersigned will pay all transfer taxes payable with respect
thereto and is delivering herewith such certificates and opinions as reasonably requested by the Company in accordance therewith.
No fee will be charged to the holder for any conversion, except for such transfer taxes, if any.

 

By the delivery of
this Notice of Conversion the undersigned represents and warrants to the Company that its ownership of the Common Stock does not
exceed the amounts specified under Section 4 of this Debenture, as determined in accordance with Section 13(d) of the Exchange
Act.

 

The undersigned agrees
to comply with the prospectus delivery requirements under the applicable securities laws in connection with any transfer of the
aforesaid shares of Common Stock.

 

	Conversion calculations:	 
	 	Date to Effect Conversion:
	 	 
	 	Outstanding Amount of Debenture to be Converted:
	 	 
	 	 
	 	Number of shares of Common Stock to be issued:
	 	 
	 	 
	 	Signature:
	 	 
	 	Name:
	 	 
	 	Address for Delivery of Common Stock Certificates:
	 	 
	 	Or
	 	 
	 	DWAC Instructions:
	 	 
	 	Broker No: ______________
	 	Account No: ____________

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