* Family backs pharma unit even if avelumab not a blockbuster
* Family rep speaking at company's 350 yr anniversary
* Merck has been looking for more development partners (Adds details on family, cancer drug, group size)
DARMSTADT, Germany, May 3 (Reuters) - The family behind Germany's Merck KGaA said it was fully committed to the diversified group's pharmaceuticals unit, even if cancer immunotherapy hopeful avelumab does not achieve blockbuster sales.
"Pharma is one of our three pillars and we absolutely stand behind it. If avelumab doesn't become a blockbuster there are enough highly interesting products in our pipeline," said family representative Frank Stangenberg-Haverkamp, speaking at an event marking the group's 350-year anniversary at its Darmstadt, Germany headquarters.
Blockbuster is the industry term for a drug with more than $1 billion in annual sales, but analysts on average do not expect avelumab, branded as Bavencio, to reach that status.
Trial results have been mixed and it faces tough competition in a class of drugs dominated by Merck & Co's Keytruda and Bristol-Myers Squibb's Opdivo.
Merck, which is developing avelumab in an alliance with Pfizer, is in intense negotiations with prospective partners for other promising experimental drugs in its pipeline.
The Merck family, which holds 70 percent of the shares, have pursued a diversified approach, with the group's activities ranging from liquid crystals for flat screens and pearlescent pigments to fertility drugs and lab equipment.
At 7 billion euros ($8.4 billion) in 2017 healthcare revenues - including allergy treatments and a consumer care unit it is selling - Merck does not make the top 20 list of global pharma majors.
Stangenberg-Haverkamp is one of two leading representatives of the roughly 150 family members that have voting rights in the family holding.
$1 = 0.8342 euros Reporting by Patricia Weiss Writing by Ludwig Burger Editing by Maria Sheahan