The younger sister of Bollywood actress Katrina Kaif is to act opposite Harsh in the project, which is being produced by crossover star Anil Kapoor.
Filmmaker Steven Roy Thomas told Digital Spy: "As director, I couldn't be more anxious and excited to bring our story to screen.
"Harsh and Isabelle are extremely talented, honest and smart actors. There's no question they have it in their blood. I'm really looking forward to working with our entire cast and crew on this special project."
The screenplay, which has the working title Coming Home, has been written by Erica Stair Reddy and Melanie Easton, from Erica and Melanie Productions.
Easton revealed: "It's got Bollywood elements but it's a short film, so that's kind of antithetical to typical Bollywood. It's about one tenth of the running time of a Hindi film, with no song breaks.
"It was originally written to be set in New York, although recently there's been some talk of re-writing to make it suitable to shoot in Mumbai. As it stands now, it's set in NYC."
She added: "We are really happy with the script and it's a great stepping stone for everyone involved to work on."
Katrina Kaif previously spoke to Digital Spy about her sister's rumoured launch into the film industry.