CAMBRIDGE — As the creators of “Les Miserables’’ knew well, lost causes and doomed rebellions can be resonant subjects for a musical, given how naturally the genre gravitates toward melodrama and a certain what-if? melancholy.

The key is to stay on the right side of the line between melancholy and torpor — and that’s a challenge “We Live in Cairo’’ fails to meet in its world premiere at the American Repertory Theater.

After a flawed but pretty absorbing Act One, the story goes utterly slack in Act Two of this musical about six young activists in the Egyptian revolution of 2011. As they join the battle to topple an authoritarian president (speaking of resonant subjects), the youthful activists weaponize Twitter, Facebook, and YouTube (one describes Facebook as, ahem, “crucial for the dissemination of truth’’). Once they achieve their goal, disappointment is not long in coming for the activists. Alas, much the same is true for the audience at “We Live in Cairo.’’

Directed by Taibi Magar, it’s the creation of brothers Daniel Lazour and Patrick Lazour, originally from Boylston, who wrote the book, music, and lyrics. The talent of the Lazours is evident — some of their tunes, expertly performed by an onstage seven-piece band, possess a hypnotic beauty — but several members of the cast lack the vocal chops to really put those songs across.


Still, partly thanks to the dynamism of Samar Haddad King’s choreography, there are times during Act One when “We Live in Cairo’’ channels some of the raw, youthful energy that suffuses musicals like “American Idiot,’’ “Rent,’’ and “Bloody Bloody Andrew Jackson.’’ Moreover, “We Live in Cairo’’ is smart about the personal and ideological fissures that can strain the solidarity within political movements, and about the nexus between activism and technology that was so crucial to the Egyptian revolution and the Arab Spring of which it was a part. Director Magar underscores the centrality of social media in the revolution via an arresting, if overly hectic, array of video projections (designed by David Bengali) rife with images of tweets (shades of “Dear Evan Hansen’’) as well as footage of demonstrations and police crackdowns.


For all the snazzy screen visuals, one can’t shake the nagging feeling that “We Live in Cairo’’ is in the wrong ART venue. Rather than the Loeb Drama Center, it seems like a better fit for the more intimate confines of Oberon, the Harvard Square club that functions as the ART’s second stage, where the company often presents smaller-scaled, immersive works.

Set in Cairo from 2011 to 2013, “We Live in Cairo’’ ranges from the early days of the Egyptian revolution, to the resignation of the autocratic Hosni Mubarak in the face of strikes and demonstrations in Tahrir Square and elsewhere, to the rise of the Muslim Brotherhood and the election of Mohamed Morsi, to the military ouster of Morsi, and beyond.

A pair of brothers occupy the center of the story: guitar-strumming singer-songwriter Amir (a soulful Jakeim Hart) and Hany (a too-tentative Abubakr Ali). Hany takes a dim view of the burgeoning romance between Amir and a young Muslim woman named Layla (a vibrant Parisa Shahmir). For graffiti artist Karim (Sharif Afifi), a spray-paint can is his favored instrument of opposition; the same becomes true for Hassan (Gil Perez-Abraham), whom Karim is attracted to. The firebrand and conscience of the group is Fadwa, who has spent time in jail for participating in a sit-in. Fadwa’s introductory song is “Loud Voice’’ (“I’m the one with the loud voice’’), and Dana Saleh Omar, who portrays her, follows suit with an overly shouty performance.


For all six of these activists, the price of protest grows progressively steeper. It becomes a struggle to hold on to their early idealism, passion, and sense of unity, captured in the early song “Genealogy of Revolution,’’ with its rousing refrain “Go to the square/Go to the square/ You’ll know the words when you are there.’’

However, virtually all of that atmospheric urgency is gone by the end of the talky, anticlimactic second act of “We Live in Cairo,’’ when one static sequence follows another as the activists add up their losses, lament the present, and mull the future. Revolutionaries are often at a loss when a revolution is over; similarly, it becomes clear that the musical’s creators have not figured out a way to make post-revolution disillusionment dramatically compelling. Act Two plays like one long epilogue. Still, “We Live in Cairo’’ does furnish reason to believe that it will be a prologue to another, more complete musical from the Lazour brothers down the road.


Book, music, and lyrics by Daniel Lazour & Patrick Lazour. Directed by Taibi Magar. Presented by American Repertory Theater. At Loeb Drama Center, Cambridge, through June 16. Tickets from $25, 617-547-8300, www.americanrepertorytheater.org


Don Aucoin can be reached at aucoin@globe.com. Follow him on Twitter@GlobeAucoin