* Tyler Lessard leaves to "pursue other interests"
* Replacement Alec Saunders previously worked for QNX
* Source confirms departure of Jeff McDowell (Adds confirmation of McDowell departure)
TORONTO, Sept 29 (Reuters) - Executives in charge of developer relations and business outreach at Research In Motion RIM.TO have left the company, the latest in a string of departures this year as the BlackBerry maker trims its workforce.
Tyler Lessard, the company's senior vice-president for global alliances and developer relations, "is moving on to pursue other interests," RIM said in a statement on Thursday.
A source with direct knowledge of the situation told Reuters that Jeff McDowell, senior vice-president for platform marketing and alliances, left the company two months ago.
Both exits were first reported by the crackberry.com blog, but RIM only confirmed the departure of Lessard.
Lessard has been replaced by Alec Saunders, who once worked for QNX Software before QNX was bought by RIM.
QNX software powers RIM's PlayBook tablet computer and will be used in products RIM has dubbed "superphones", which it is set to launch next year.
McDowell, whose job was to expand RIM's global sales to businesses and to market its software and services, was a keynote speaker at RIM's BlackBerry World conference in May.
Saunders will be at RIM's developer conference next month in San Francisco, where a major PlayBook upgrade is expected to add native email and calendar functions, as well as some compatibility with Google's (GOOG.O) Android software.
Earlier on Thursday, RIM confirmed its commitment to the PlayBook and QNX after an analyst suggested the Canadian smartphone maker might walk away from the tablet market, which is dominated by Apple's iPad. [ID:nS1E78S116]
RIM has witnessed a stream of high-profile departures from its developer relations and marketing teams in recent months and in July it said it was slashing about 11 percent of its workforce due to falling sales and profit. [nL3E7IP251]
Mike Kirkup, a director of developer relations, resigned in August. RIM's head of marketing, Keith Pardy, left in March, just ahead of the PlayBook launch, and two of his staff later exited for jobs with Samsung (005930.KS), a fierce rival whose phones and tablets use Google's Android system. [ID:nN1E76J100]
A chief operating officer, Don Morrison, resigned in July after taking a medical leave.
RIM's shares were down more than 5 percent at mid-afternoon on Thursday in a broadly depressed Nasdaq market. (Editing by Peter Galloway)