The decision to hold the earnings outlook despite a better revenue picture reflects accelerated investment in research and development, the company said.
Chief Executive Pascal Soriot, who fended off a $118 billion takeover attempt by Pfizer last year, is banking on a promising pipeline of new drugs - particularly in cancer - to revive the company's sales from 2017.
Quarterly sales totalled $6.3 billion, held back by cheap copycat versions of heartburn pill Nexium, while core earnings per share, which exclude certain items, fell 8 percent to $1.21.
Industry analysts had on average forecast sales of $6.0 billion and earnings of $1.05 cents a share, according to Thomson Reuters.
Revenue from "externalisation", or the sale of rights to certain drugs, amounted to $780 million in the six months to June 30, with the largest chunk coming from a $450 million deal with Celgene.